Starter
For your first email program.
$16USD / month
$192 billed yearly.
20,000 emails / month
Choose Starter- 5 brands · 3 seats
- 5 custom sending domains
- 500 email verifications/month
- $1.50 / 1,000 extra emails
Nitrosend is the best email service provider for teams that run email from AI, with the top score of 76.5 out of 100 and 9 out of 10 on working from your AI assistant, one of the two tests worth the most points. To run it from Claude, ChatGPT, Cursor or Codex, add Nitrosend's MCP server at api.nitrosend.com/mcp and sign in with OAuth, so there is no API key to paste (setup guide). It writes each email in your brand's colors, fonts and voice and sends it once you approve it. Your newsletters and your receipts go out from one account on one bill, and contacts are unlimited on every plan. It also costs the least: $20 a month for 20,000 emails and $650 for a million emails on Scale including overage, the lowest paid price among the seven at both volumes. Brevo comes next, at 74.
The ranking
Rank 1Nitrosend
76.5 out of 100Total
- Priced by
- Emails sent
- Free plan
- 5,000 emails, then 500 a month
- Entry plan
- $20 a month, 20,000 emails
- Works from your AI assistant9 out of 10Official MCP server runs campaigns, flows and sends from the chat; campaigns and flows stay drafts until approved (MCP registry).
- Emails in your brand, no designer9 out of 10Brand Kit scans the site for colors, fonts and voice, and applies them to every draft on every plan (docs).
- Price8.5 out of 10Unlimited contacts on every plan. $20 a month for 20,000 emails and $650 for a million emails on Scale including overage (pricing).
- Free plan7 out of 105,000 emails to start, then 500 a month, unlimited contacts. New accounts start at 100 recipients per rolling 24 hours (pricing).
- Receipts and newsletters on one plan9 out of 10Transactional and marketing email share one allowance and one API on every plan, Free included (pricing).
- Editor for building by hand6 out of 10A block builder exists for editing by hand, but it is plainer, because the agent is the main way in.
- Integrations, support and track record5 out of 10Shopify, Stripe, HubSpot, Attio and Mailchimp, five bring-your-own sending providers, a Node SDK, a CLI and signed webhooks for transactional email, but a young product from a small team (docs).
Nitrosend
Ask your agent for the next campaign
Connect Nitrosend to Claude, ChatGPT, Cursor or Codex, point Brand Kit at your site, and describe the email. Contacts are unlimited on every plan.
Free: 5,000 emails to start, then 500 a month. No credit card.
Start free
Rank 2Brevo
74 out of 100Total
- Priced by
- Emails sent
- Free plan
- 300 emails a day, 100,000 contacts
- Entry plan
- $9 a month, 5,000 emails
- Works from your AI assistant7 out of 10Official MCP server manages campaigns, contacts and templates, but lists no module for automations (Brevo developers).
- Emails in your brand, no designer7 out of 10Brand library fetches logo, colors, fonts and links from your site into the editor, not voice (Brevo help).
- Price6 out of 10Priced by emails sent. $69 a month for 20,000 on Standard, $32 on Starter without automation, and $999 for a million on Professional (pricing).
- Free plan8 out of 10300 emails a day, up to 100,000 contacts, transactional email included, free forever (Brevo help).
- Receipts and newsletters on one plan9 out of 10Every plan, Free included, has transactional email by API and SMTP in the same volume (pricing FAQ).
- Editor for building by hand8 out of 10Drag-and-drop editor and templates, 4.5 of 5 across 2,722 reviews, Ease of Use the top tag (G2).
- Integrations, support and track record8 out of 10150+ integrations, SMS, WhatsApp and a CRM in one account, phone support on Professional (pricing).
Rank 3Klaviyo
64 out of 100Total
- Priced by
- Active profiles
- Free plan
- 250 profiles, 500 emails a month
- Entry plan
- $20 a month, 500 profiles
- Works from your AI assistant8 out of 10Official remote MCP server with more than 300 tools, including
send_campaignandcreate_flow(Klaviyo developers). - Emails in your brand, no designer7 out of 10Brand library detects logos, colors, buttons and fonts from your site, but not voice (Klaviyo help).
- Price2 out of 10Billed by active profiles. $150 a month at 10,000, and 500,000 is by quote (pricing).
- Free plan4 out of 10250 active profiles and 500 emails a month, with email support for 60 days (pricing).
- Receipts and newsletters on one plan6 out of 10Transactional runs as approved flow messages on the same plan, with each message reviewed by Klaviyo first (help).
- Editor for building by hand9 out of 10Mature editor and flow builder, 4.6 of 5 across 1,362 reviews, Ease of Use the top tag (G2).
- Integrations, support and track record9 out of 10400+ pre-built integrations, deep Shopify data, and SMS, WhatsApp and reviews in one account (Klaviyo).
Rank 4MailerLite
61.5 out of 100Total
- Priced by
- Subscribers
- Free plan
- 250 subscribers, 2,500 emails a month
- Entry plan
- $12 a month, 500 subscribers
- Works from your AI assistant8 out of 10Official MCP server with
create_campaign,schedule_campaignandcreate_automationtools (MailerLite help). - Emails in your brand, no designer7 out of 10Brand styles pull logo, colors, fonts and links from your site's URL, but not voice (MailerLite help).
- Price3 out of 10Priced by subscribers. $89 a month at 10,000 on Comfort, and a quote above 200,000, where Comfort is $819 (pricing).
- Free plan5 out of 10250 subscribers and 2,500 emails a month, with 3 automations and knowledge base support (pricing).
- Receipts and newsletters on one plan5 out of 10Transactional email is MailerSend, a separate product the pricing table links out to (pricing).
- Editor for building by hand8 out of 10Three editors on every plan, drag-and-drop included, and 4.6 of 5 across 1,113 reviews (G2).
- Integrations, support and track record7 out of 10100+ integrations, sites and landing pages built in, and 24/7 live chat on Power (pricing).
Rank 5Mailchimp
59 out of 100Total
- Priced by
- Contacts held
- Free plan
- 250 contacts, 500 sends a month
- Entry plan
- $13 a month, 500 contacts
- Works from your AI assistant5 out of 10Its Claude and ChatGPT app drafts campaigns, but Mailchimp's own guide says to finish and send in the web app (Mailchimp).
- Emails in your brand, no designer7 out of 10Brand Kit pulls fonts from your site and generates on-brand layouts, on Essentials and above only (Mailchimp help).
- Price3 out of 10Priced by contacts. $110 a month at 10,000 on Essentials, $135 on Standard, and a quote at 500,000 (pricing).
- Free plan4 out of 10250 contacts and 500 sends a month, with at most 250 a day (Mailchimp help).
- Receipts and newsletters on one plan5 out of 10Transactional is a separate add-on for Standard and Premium, at $20 per 25,000 emails (pricing).
- Editor for building by hand9 out of 10Mature drag-and-drop editor and templates, the most common praise from reviewers, 4.3 of 5 across 12,990 reviews (G2).
- Integrations, support and track record9 out of 10300+ integrations, 24/7 support on paid plans, phone support on Premium, and two decades at scale (pricing).
Rank 6ActiveCampaign
58.5 out of 100Total
- Priced by
- Contacts held
- Free plan
- None, a 14-day trial
- Entry plan
- $15 a month, 1,000 contacts, billed annually
- Works from your AI assistant8 out of 10Official MCP server creates a campaign and sends or schedules it once you approve its summary in the chat, and manages contacts, lists, tags and automations (tools).
- Emails in your brand, no designer7 out of 10AI Brand Kit imports colors, fonts and logos from your URL and builds templates in its editor (ActiveCampaign).
- Price2 out of 10Priced by contacts. Starter is $149 a month at 10,000, billed yearly because no monthly price is published, and above 50,000 it is by quote (pricing).
- Free plan1 out of 10No free plan. A 14-day trial with up to 100 email sends (help).
- Receipts and newsletters on one plan5 out of 10Transactional email is Postmark, a separate product with its own account and bill, linked by an app (ActiveCampaign).
- Editor for building by hand8 out of 10Mature email designer and automation builder, 4.4 of 5 across 14,799 reviews (G2).
- Integrations, support and track record9 out of 101,000+ apps and integrations, premium Salesforce and Dynamics connectors, and a built-in CRM (apps).
Rank 7Constant Contact
51.5 out of 100Total
- Priced by
- Contacts held
- Free plan
- None, a trial with 100 sends
- Entry plan
- $12 a month, 500 contacts
- Works from your AI assistant5 out of 10Its Claude connector drafts and previews emails, then hands you a link to finish sending in Constant Contact (help).
- Emails in your brand, no designer7 out of 10BrandKit scans your website for logo, colors and images, but not voice (help).
- Price3 out of 10Priced by contacts. $120 a month at 10,000 on Lite, $160 on Standard, and a quote above 50,000 (pricing).
- Free plan1 out of 10No free plan. The trial allows up to 100 email sends in total (help).
- Receipts and newsletters on one plan2 out of 10Its community manager says it is not designed for transactional email and has no transactional API (community).
- Editor for building by hand8 out of 10Hundreds of templates and a drag-and-drop editor, 4.1 of 5 across 7,536 reviews (G2).
- Integrations, support and track record9 out of 10About 300 integrations, events, SMS and social tools, and phone support (pricing).
How they compare
How each one scores
Scores out of 10, November 10, 2026| What we compared | Nitrosend | Brevo | Klaviyo | MailerLite | Mailchimp | ActiveCampaign | Constant Contact |
|---|---|---|---|---|---|---|---|
| Works from your AI assistant20 points | 9 out of 10 | 7 out of 10 | 8 out of 10 | 8 out of 10 | 5 out of 10 | 8 out of 10 | 5 out of 10 |
| Emails in your brand, no designer10 points | 9 out of 10 | 7 out of 10 | 7 out of 10 | 7 out of 10 | 7 out of 10 | 7 out of 10 | 7 out of 10 |
| Price20 points | 8.5 out of 10 | 6 out of 10 | 2 out of 10 | 3 out of 10 | 3 out of 10 | 2 out of 10 | 3 out of 10 |
| Free plan10 points | 7 out of 10 | 8 out of 10 | 4 out of 10 | 5 out of 10 | 4 out of 10 | 1 out of 10 | 1 out of 10 |
| Receipts and newsletters on one plan10 points | 9 out of 10 | 9 out of 10 | 6 out of 10 | 5 out of 10 | 5 out of 10 | 5 out of 10 | 2 out of 10 |
| Editor for building by hand15 points | 6 out of 10 | 8 out of 10 | 9 out of 10 | 8 out of 10 | 9 out of 10 | 8 out of 10 | 8 out of 10 |
| Integrations, support and track record15 points | 5 out of 10 | 8 out of 10 | 9 out of 10 | 7 out of 10 | 9 out of 10 | 9 out of 10 | 9 out of 10 |
| Total scoreout of 100 | 76.5 out of 100,1st | 74 out of 100,2nd | 64 out of 100,3rd | 61.5 out of 100,4th | 59 out of 100,5th | 58.5 out of 100,6th | 51.5 out of 100,7th |
Here are the seven yes-or-no questions people usually ask before they choose an email service provider. A tick means the platform does it, as described on its own pages today. A dash means the answer is not a clean yes or no.
7 services, side by side
Checked November 10, 2026QuestionNitrosendBrevoKlaviyoMailerLiteMailchimpActiveCampaignConstant Contact
NitrosendBrevoKlaviyoMailerLiteMailchimpActiveCampaignConstant ContactSend a campaign from the chatCan an agent send a marketing campaign without anyone opening the web app?Nitrosend: Yes.Brevo: Not a yes or no.Klaviyo: Yes.MailerLite: Yes.Mailchimp: No.ActiveCampaign: Yes.Constant Contact: No.
| Service | Answer |
|---|---|
| Nitrosend | Yes. Yes, through the MCP server. Campaigns stay drafts until approved. |
| Brevo | Not a yes or no. Its MCP server creates and manages email campaigns. Its docs list no module for automations. |
| Klaviyo | Yes. Yes. The official MCP server has a send_campaign tool. |
| MailerLite | Yes. Yes. Its MCP server can create and schedule campaigns. |
| Mailchimp | No. Not yet. Its Claude and ChatGPT app drafts the campaign, and Mailchimp's own guide has you finish and send in the web app. |
| ActiveCampaign | Yes. Yes, once you approve its summary in the chat. |
| Constant Contact | No. No. Claude hands you a link to finish sending in Constant Contact. |
Official MCP serverIs there a first-party MCP server for marketing email?Nitrosend: Yes.Brevo: Yes.Klaviyo: Yes.MailerLite: Yes.Mailchimp: Not a yes or no.ActiveCampaign: Yes.Constant Contact: Yes.
| Service | Answer |
|---|---|
| Nitrosend | Yes. Yes. Listed as com.nitrosend/nitrosend on the official MCP registry. |
| Brevo | Yes. Yes, remote-hosted, with 27 modules. |
| Klaviyo | Yes. Yes, remote-hosted, with more than 300 tools. |
| MailerLite | Yes. Yes. It can also build automations, with create_automation. |
| Mailchimp | Not a yes or no. Official Claude and ChatGPT app and connectors on Standard and above. The only official MCP server covers Transactional. |
| ActiveCampaign | Yes. Yes, a remote MCP URL on every plan. |
| Constant Contact | Yes. Yes, as an official Claude connector, plus a ChatGPT app. |
Brand kit from your siteDoes it pick up your logo, fonts and colors from your website?Nitrosend: Yes.Brevo: Yes.Klaviyo: Yes.MailerLite: Yes.Mailchimp: Yes.ActiveCampaign: Yes.Constant Contact: Yes.
| Service | Answer |
|---|---|
| Nitrosend | Yes. Yes. Brand Kit reads colors, fonts and voice from your site. |
| Brevo | Yes. Yes. The brand library fetches logo, colors, fonts and links. |
| Klaviyo | Yes. Yes. The brand library detects logos, colors, buttons and fonts. |
| MailerLite | Yes. Yes. Brand styles pull logo, colors, fonts and links. |
| Mailchimp | Yes. Yes, on Essentials and above. |
| ActiveCampaign | Yes. Yes, with the AI Brand Kit. |
| Constant Contact | Yes. Yes. BrandKit scans for logo, colors and images. |
Rarely emailed contacts are freeDoes holding a contact you rarely email cost nothing?Nitrosend: Yes.Brevo: Yes.Klaviyo: No.MailerLite: No.Mailchimp: No.ActiveCampaign: No.Constant Contact: No.
| Service | Answer |
|---|---|
| Nitrosend | Yes. Yes. Contacts are unlimited on every plan. |
| Brevo | Yes. Yes. The bill follows emails sent. |
| Klaviyo | No. No. Every active profile counts toward the plan. |
| MailerLite | No. No. The plan is set by subscriber count. |
| Mailchimp | No. No. Every contact counts toward the tier, unsubscribed and non-subscribed ones included. |
| ActiveCampaign | No. No. The plan is set by how many contacts you hold. |
| Constant Contact | No. No. The plan is set by contact count. |
Transactional includedAre receipts and resets in the same plan as newsletters?Nitrosend: Yes.Brevo: Yes.Klaviyo: Not a yes or no.MailerLite: No.Mailchimp: No.ActiveCampaign: No.Constant Contact: No.
| Service | Answer |
|---|---|
| Nitrosend | Yes. Yes, on every plan including Free. |
| Brevo | Yes. Yes, on every plan including Free. |
| Klaviyo | Not a yes or no. Through approved, metric-triggered flows rather than a send call. |
| MailerLite | No. No. Transactional is MailerSend, a separate product. |
| Mailchimp | No. Add-on to Standard or Premium, $20 per 25,000 emails. |
| ActiveCampaign | No. No. Transactional is Postmark, billed separately. |
| Constant Contact | No. No. It is not built for transactional email. |
Free plan with no time limitIs there a free plan that does not expire?Nitrosend: Yes.Brevo: Yes.Klaviyo: Yes.MailerLite: Yes.Mailchimp: Yes.ActiveCampaign: No.Constant Contact: No.
| Service | Answer |
|---|---|
| Nitrosend | Yes. Yes. 5,000 emails to start, then 500 a month. |
| Brevo | Yes. Yes, 300 emails a day. |
| Klaviyo | Yes. Yes, up to 250 active profiles and 500 emails a month. |
| MailerLite | Yes. Yes, with a cap on subscribers and on emails a month. |
| Mailchimp | Yes. Yes, up to 250 contacts. |
| ActiveCampaign | No. No. A 14-day trial with up to 100 sends. |
| Constant Contact | No. No. A trial with up to 100 sends. |
Mature drag-and-drop editorIs there a polished visual editor for a person building by hand?Nitrosend: Not a yes or no.Brevo: Yes.Klaviyo: Yes.MailerLite: Yes.Mailchimp: Yes.ActiveCampaign: Yes.Constant Contact: Yes.
| Service | Answer |
|---|---|
| Nitrosend | Not a yes or no. A block builder exists. The agent is the main way in. |
| Brevo | Yes. Yes, with templates and a brand library. |
| Klaviyo | Yes. Yes, and reviewers rate it highly. |
| MailerLite | Yes. Yes, plus custom HTML and simple editors. |
| Mailchimp | Yes. Yes, and reviewers rate it highly. |
| ActiveCampaign | Yes. Yes, and a mature automation builder. |
| Constant Contact | Yes. Yes, with hundreds of templates. |
Yes answersOut of the questions that have a yes or no for that service6 of 6 yes for Nitrosend6 of 6 yes for Brevo5 of 6 yes for Klaviyo5 of 7 yes for MailerLite3 of 6 yes for Mailchimp4 of 7 yes for ActiveCampaign3 of 7 yes for Constant Contact
At a glance
7 services, the same 7 tests, 100 points in all. In order: Nitrosend 76.5, Brevo 74, Klaviyo 64, MailerLite 61.5, Mailchimp 59, ActiveCampaign 58.5, Constant Contact 51.5. Nitrosend has the best score on Works from your AI assistant, Emails in your brand, no designer, Price and Receipts and newsletters on one plan. Every price and feature was read on each company's own pages on November 10, 2026.
When another ESP is the better pick
Nitrosend does not win every test. Read these before you choose it.
- Pick Brevo if you hold a large list and mail it rarely. It bills on emails sent rather than contacts held, sends receipts on the same plan, and its free plan is 300 emails a day with no time limit. It beats Nitrosend on free plan, 8 to 7, on the editor, 8 to 6, and on integrations and track record, 8 to 5. Automation starts on Standard, $69 a month at 20,000 emails. The Brevo alternatives page covers where it falls short.
- Pick Klaviyo if you run an online store at scale. It scores 9 on the editor and 9 on integrations and track record, and its MCP server lists a send_campaign tool that sends a campaign to its audience from the chat. It bills on active profiles, $150 a month at 10,000. The Nitrosend and Klaviyo comparison scores the two head to head.
- Pick MailerLite if your list is small and you want the fastest editor to learn. It scores 8 on the editor, and its MCP server can create and schedule campaigns and draft automations. Comfort is $89 a month at 10,000 subscribers. More on the MailerLite alternatives page.
- Pick Mailchimp if you need an integration only it has. It scores 9 on the editor and 9 on integrations and track record. Essentials is $110 a month at 10,000 contacts and Standard $135, and unsubscribed and non-subscribed contacts count toward the tier. The Nitrosend and Mailchimp comparison has the detail, and so does the Mailchimp alternatives page.
- Pick ActiveCampaign if automation is the product. It scores 9 on integrations and track record and 8 on the editor, with a mature automation builder. Starter is $149 a month at 10,000 contacts, billed yearly, and there is no free plan.
- Pick Constant Contact if you want a template-led editor and a long track record. It scores 9 on integrations and track record and 8 on the editor, with hundreds of templates. Lite is $120 a month at 10,000 contacts, and there is no free plan.
What each one costs in 2026
Five of the seven charge for every contact you hold, whether you email it or not: Klaviyo, ActiveCampaign, MailerLite, Mailchimp and Constant Contact. Brevo and Nitrosend charge for the emails you send, and Nitrosend does not charge for contacts at all.
What sending costs
List prices, USD, monthly, November 10, 2026| Service | 20,000 emails a month | 1,000,000 emails a month |
|---|---|---|
| Nitrosend (pricing page) | $20Starter, contacts unlimited | $650Scale, contacts unlimited, including overage |
| Brevo (pricing page) | $69Standard, the first plan with automation. Starter is $32 without it | $999Professional. Standard stops at 500,000 emails |
| Klaviyo (pricing page) | $150Email, 10,000 active profiles | Ask salesBy quote. The published slider stops at 150,000 profiles, $1,955 |
| MailerLite (pricing page) | $89Comfort, 10,000 subscribers | Ask salesEnterprise, by quote. Published tiers stop at 200,000, $819 on Comfort |
| Mailchimp (pricing page) | $110Essentials, flows up to 4 steps. Standard is $135 | Ask salesPremium only, by quote. Published tiers stop at 200,000 contacts |
| ActiveCampaign (pricing page) | $149Starter, billed yearly, 5 actions per automation | Ask salesBy quote. Published tiers stop at 50,000 contacts |
| Constant Contact (pricing page) | $120Lite, one automation template. Standard is $160 | Ask salesBy quote. Published tiers stop at 50,000 contacts |
At 20,000 emails a month, a 10,000-contact list emailed twice, Nitrosend is $20. Brevo is $69 on Standard, MailerLite $89, Mailchimp $110, Constant Contact $120, ActiveCampaign $149 billed yearly and Klaviyo $150.
At a million emails a month, Nitrosend is $650. Brevo is $999 on Professional, because Standard stops at 500,000 emails. The other five publish no price at 500,000 contacts, so the answer is a sales call. What email marketing really costs has the wider math.
The bigger difference is what the $20 buys. The Nitrosend pricing page puts contacts at unlimited on every plan, and receipts and newsletters draw on the same allowance. If you would otherwise pay one provider for campaigns and a second for transactional email, add the two bills together before you compare.
How we scored
Every platform gets a score out of 10 on the same seven tests. Each test is worth a set number of points, 100 in all. Working from your AI assistant and price are worth the most, 20 points each, because that is where email marketing is heading and what decides the bill every month. The editor and the track record, where the older providers are strongest, share 30 points, so a provider that is better there gets full credit for it.
The AI test starts with who publishes the server. The official MCP registry only lets a company publish under its own reverse-domain name after proving it controls that domain, so Nitrosend's server is listed as com.nitrosend/nitrosend. A search there for Klaviyo on October 2, 2026 returned three servers, all published by other companies, while Klaviyo's own is documented on its developer site. A third-party server holds your account key, so the tests here score only servers the provider publishes itself.
Each test is a question with one answer per service, checked against the service's own pages on November 10, 2026. A 10 means it does the job fully on its normal plans. A 5 means it does part of it, or only on a higher plan or in a second product.
Works from your AI assistant, 20 points. Can an agent inside Claude, ChatGPT, Cursor or Codex compose a marketing campaign, test it, and send it, with no person opening the web app between the prompt and the send? An approval step the person answers in the chat counts as inside the agent. Moving into the web app to finish does not. Scored on one written rule for every vendor: a first-party server the vendor runs and that can send counts fully; a third-party wrapper (Zapier, Composio, Kanopi, community servers) counts for less; a server that only drafts or reads counts for less than one that sends.
Emails in your brand, no designer, 10 points. Does the product learn your logo, colors, fonts and voice from your own site and apply them to every email it drafts, on the plan most small teams start on?
Price, 20 points. What does email cost each month at 20,000 emails, a 10,000-contact list emailed twice, and at 1,000,000, a 500,000-contact list emailed twice? Scored on list prices in US dollars, paid monthly, at the cheapest plan that holds the contacts, covers the sends and includes automated emails such as a welcome series. Every ranking on this site uses the same fixed scale. At 20,000 emails, $20 or less scores 10, then $25 scores 9, $32 scores 8, $40 scores 7, $50 scores 6, $70 scores 5, $100 scores 4 and $140 scores 3. At 1,000,000, $500 or less scores 10, then $625, $800, $1,000, $1,250, $1,750, $2,500 and $3,500 step down the same way. Anything dearer, or a price given only by quote, scores 2. A free product scores 10. The score is the average of the two.
Free plan, 10 points. How far can a team get on the free plan before it has to pay: contacts, total sends, and the daily ceiling.
Receipts and newsletters on one plan, 10 points. Can receipts, password resets and newsletters go out from one account, on one bill, through one API?
Editor for building by hand, 15 points. For a person who wants to build the email themselves: how mature are the visual editor and the template library?
Integrations, support and track record, 15 points. How many tools does it plug into, what support comes with the plan, and how long has it been doing this at scale?
One thing is not scored: inbox placement. None of these providers publishes a comparable deliverability number, so a score there would be a guess dressed up as a measurement.
What an ESP actually does
Four things, and every platform on this list does all four to some degree.
- List management. Collecting addresses, storing consent, and cutting the list into segments you can send to.
- Campaign creation. A template system and an editor, so a send does not need a developer.
- Automation. Welcome series, cart reminders and behavior-triggered journeys that run without you.
- Analytics. Opens, clicks, bounces and complaints, the numbers that keep you out of the spam folder.
The part people underrate is underneath. An ESP lets you send from your own domain rather than a personal mailbox, which is what keeps deliverability intact as volume climbs. An ESP is also not cold outreach infrastructure. Cold prospecting and marketing email run on different domains, mailboxes, volumes and deliverability rules, and none of the seven platforms here is a cold outreach tool.
One piece of advice for every new sender: do not pay for a dedicated IP at low volume. Below a couple of hundred thousand emails a month there is not enough traffic to build a reputation on an IP of your own, and a well-run shared pool will place mail better. Postmark, for one, gives a dedicated IP only to senders of at least 300,000 messages a month and says a pristine shared pool gives most people the best results.
Which ESP is best for a small business with a list under 5,000?
Nitrosend, if you want an AI assistant to draft and send while you approve, because the $20 Starter plan covers 20,000 emails a month whatever the list size. MailerLite if you want the fastest editor to learn and will build the emails yourself. Brevo if your list is large relative to how often you send, since it bills on volume rather than contacts. Constant Contact if you want a template-led editor. Mailchimp if you need an integration that only it has. Check how each one counts a contact before you compare prices, because the counting method decides the bill more than the headline rate does.
Do I need an ESP if I already send from Gmail or Outlook?
Yes, once you send the same message to more than a handful of people. Gmail and Outlook are mailboxes, with daily sending caps (a personal Gmail account stops at 500 emails a day, and Google Workspace at 2,000 per user), no consent tracking, no unsubscribe handling and no bounce reporting, and bulk sending from them puts your normal business mail at risk. An ESP sends from your own verified domain with authentication, suppression lists and a one-click unsubscribe, which is what the mailbox providers now require. Gmail wants one-click unsubscribe on marketing mail from anyone sending more than 5,000 messages a day to its users, and Yahoo asks senders to honor an unsubscribe within 2 days. An ESP handles both; a mailbox does neither.
The reverse holds for one-to-one outreach. George Hartley, Nitrosend's co-founder, explained on SaaS Stories in September 2026 that "outbound actually sort of has to run from email addresses, right? You can't run outbound through a bulk system because that's immediately going to cook everything like Gmail will just cut you off." So use an ESP for anything you send to a list, and keep personal outreach in real mailboxes.
Can one ESP handle both my marketing email and my password resets?
Two of the seven do it on one plan: Nitrosend and Brevo. Klaviyo sends transactional email through metric-triggered flows that Klaviyo approves, which can take up to a business day, and editing an approved message removes its transactional status until it is approved again. That matters once an assistant is editing your receipts: every wording change reopens the review. Mailchimp sells it as an add-on to Standard or Premium, ActiveCampaign sends it through Postmark by ActiveCampaign, and MailerLite through MailerSend, a separate product. What matters as much as the checkbox is whether the two streams are kept apart, so a Tuesday newsletter cannot delay a password reset. Nitrosend's pricing page lists stream separation for transactional and marketing mail. Transactional email compared with marketing email sets out the two jobs, and the email API page covers the sending side. The best email API services review ranks the providers built for the transactional half.
How to move to a new ESP without losing deliverability
The import is the easy half. The reputation is the half that breaks.
- Export contacts and engagement history together. Engagement history is what lets you warm the new sender on people who actually open things.
- Clean what you exported. A bad list does not become clean by changing platforms, and the email blacklist checker shows what you are carrying.
- Authenticate the new sender on your domain. List both senders in one SPF record during the overlap. The email authentication page has the records.
- Warm up rather than switching in one send. How to warm up an email domain has the ramp. Your old provider's IP addresses do not come with you, so the new sender starts without history, and Postmark notes that every mailbox provider has its own limit on how much mail it accepts at once from a new sender. Stay on the shared pool unless you send several hundred thousand emails a month.
- Send to your most engaged segment first. Widen only once bounce and complaint rates hold, and run an inbox test before the first large send.
- Rebuild the automations that earn money first. Flows do not import between platforms, which is the migration cost nobody quotes.
Email service providers FAQ
An email service provider is software that sends, tracks and manages marketing and transactional email from a domain you own. It handles list storage and consent, templates, automated sequences, and the reporting on opens, clicks, bounces and complaints. It is different from a mailbox like Gmail or Outlook, which is built for one-to-one conversations and has no consent tracking, no unsubscribe handling and a hard daily send cap.
Nitrosend, with the top score in this review, 76.5 out of 100. It runs from your AI assistant, writes in your brand, sends newsletters and receipts on one plan and costs $20 a month for 20,000 emails. Pick Brevo for a large list mailed rarely, Klaviyo for a store, MailerLite for a small list and a simple editor, Mailchimp for its integrations, ActiveCampaign for automation depth and Constant Contact for events.
Deliverability is mostly your list and your authentication, not the logo on the dashboard. All seven here can place mail in the inbox if your domain is authenticated and your list is engaged, and all seven will fail if it is not. What differs is what a provider does when something goes wrong, whether it warns you before it acts, and whether you keep your reporting when it does. What is email deliverability and deliverability rate cover the measures.
Several, with different shapes. Brevo is free to 300 emails a day with no time limit. MailerLite is free to 250 subscribers and 2,500 emails a month. Klaviyo is free to 250 active profiles and 500 emails a month, and Mailchimp to 250 contacts and 500 sends. Nitrosend gives 5,000 emails to start, then 500 a month, with unlimited contacts and full API, MCP and CLI access. ActiveCampaign and Constant Contact offer trials only.
Both, and the two models produce very different bills. Mailchimp, Klaviyo, ActiveCampaign, MailerLite and Constant Contact charge by contact. Brevo and Nitrosend charge by send, and Nitrosend does not charge for contacts at all on any plan. If you hold a large list and email it monthly, per-send pricing is far cheaper. If you email a small list daily, per-contact pricing can come out ahead.
Nitrosend, which scores 9 out of 10 on working from your AI assistant, ahead of Klaviyo, MailerLite and ActiveCampaign on 8. Most of the seven can be run from Claude or ChatGPT to some degree, and the difference is how far the assistant can go and where the brake sits. Klaviyo's tool list includes a send_campaign tool, and the way to stop it sending unasked is a setting in your chat client that blocks or asks before any tool that writes. MailerLite's server can schedule a campaign. ActiveCampaign's published tool list includes a tool that sends or schedules a prepared campaign once you approve its summary in the chat. Brevo's creates and manages campaigns, Constant Contact's Claude connector hands you a link to finish in its app, and Mailchimp's app drafts the campaign for you to send in the web app. In Nitrosend the brake is on the server: the tools that write, review and test a campaign never send it, approval is a separate step, and a send to every contact needs one more explicit confirmation. What is MCP and agentic email explain the terms.
Add the MCP server at api.nitrosend.com/mcp as a connector in Claude (or run claude mcp add --transport http nitrosend https://api.nitrosend.com/mcp in Claude Code) and sign in with OAuth. Then describe the email: Claude reads your Brand Kit, drafts the campaign in your colors and voice, can send a test to you first, and waits for your approval before anything reaches your list. The same server works in ChatGPT, Cursor and Codex. The MCP setup guide has the steps for each.
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