I am Kam Low, CTO at Nitrosend. Nitrosend is in this table. Every capability column below is checked against vendor documentation and public API specs rather than marketing pages, and the date is on each table.
Capability matrix
Core capabilities
Checked 3 September 2026| Provider | Transactional | Marketing | SMTP | Inbound | Native MCP |
|---|---|---|---|---|---|
| Nitrosend Agent-native | Yes | Yes | No | No | Yes |
| Resend | Yes | Limited | Yes | Yes | Yes |
| Postmark | Yes | No | Yes | Yes | No |
| Amazon SES | Yes | No | Yes | Yes | No |
| SendGrid | Yes | Separate product | Yes | Yes | No |
| Mailgun | Yes | Limited | Yes | Yes | No |
| MailerSend | Yes | Limited | Yes | Yes | No |
| Loops | Yes | Yes | No | No | No |
| Brevo | Yes | Yes | Yes | No | No |
| AgentMail | Yes | No | No | Yes | Yes |
Two columns deserve a note, because they are where teams get surprised.
SMTP. Nitrosend's server-side path is the REST API and we do not offer an SMTP submission relay. If a legacy system needs SMTP, run SES or Postmark underneath us with bring-your-own sending keys, or use them directly. The tradeoffs are on SMTP vs API email services.
Inbound. Nitrosend is a sender-side product. We do not receive or parse inbound email. If your application needs an inbox, Mailgun, Postmark and AgentMail all do this properly and we are not a candidate.
Developer experience
SDKs, docs and events
Checked 3 September 2026| Provider | Official SDKs | Signed webhooks | Idempotency | Sandbox / test send |
|---|---|---|---|---|
| Nitrosend 28 agent tools | Node, TypeScript, CLI | Yes | Yes | Yes |
| Resend | Node, Python, PHP, Ruby, Go, Rust, Java | Yes | Yes | Yes |
| Postmark | Node, Python, PHP, Ruby, Go, .NET, Java | Yes | No | Yes |
| Amazon SES | All AWS SDKs | Via SNS | Yes | Yes |
| SendGrid | Node, Python, PHP, Ruby, Go, C#, Java | Yes | No | Yes |
| Mailgun | Node, Python, PHP, Ruby, Go, Java | Yes | No | Yes |
| MailerSend | Node, Python, PHP, Ruby, Go, Java | Yes | No | Yes |
| Loops | Node | Yes | No | Yes |
| Brevo | Node, Python, PHP, Ruby, Java | Yes | No | Yes |
| AgentMail | Node, Python | Yes | No | Yes |
Resend genuinely wins this section. We ship @nitrosend/sdk on npm for Node and TypeScript plus a CLI, and @nitrosend/ai-sdk, which wraps our remote MCP server as Vercel AI SDK tools so an agent can send email, manage contacts, build flows and run campaigns. That is a narrower language footprint than Resend or Postmark. If your backend is Ruby or Go and you want a first-party SDK, that is a real gap and you should weigh it.
Pricing, and the part pricing pages leave out
Every provider's pricing page is honest about the tier and silent about the cliff. Two things are worth modelling before you commit.
Per-send versus per-contact. Platforms that charge per contact are cheap if you mail a small list often and expensive if you store a large list and mail a fraction of it. Platforms that charge per send are the reverse. Nitrosend charges per send with unlimited contacts, which is the right model for a large dormant list and the wrong one for a tiny list mailed daily.
Tier boundaries are cliffs, not slopes. Nick, who does our pricing analysis, framed the problem exactly: paying $500 to send 1,999,999 emails feels good, but paying $1,000 to send 2,000,001 stings, because you pay the same as someone sending 3,999,999. Every banded plan in this table has that shape. Find where your volume sits relative to the boundary before you sign, because being just over a line is the most expensive place to be. We think our own banding gets less sensible at the four-million tier, where the options collapse to a fixed price or a custom quote, and that is a fair criticism of us rather than of the category.
The BYO arbitrage. If you have engineering capacity, running your own Mailgun or SES underneath a lightweight platform layer can cut sending cost by 70 to 80% at scale. At 100,000 contacts mailed twice a month, raw sending through SES or Mailgun runs roughly $0.80 to $1.00 per 1,000 emails, so around $160 a month in sending, against several hundred on a bundled marketing platform. That is why we support BYO keys rather than fighting it.
Entry pricing
Checked 3 September 2026, confirm on vendor pages| Provider | Free tier | Paid from | Model |
|---|---|---|---|
| Nitrosend Unlimited contacts | 8,000 then 500/mo | $20/mo for 20K | Per send |
| Resend | 3,000/mo | $20/mo for 50K | Per send |
| Postmark | Trial only | $15/mo for 10K | Per send |
| Amazon SES | Tiered | $0.10 per 1,000 | Per send |
| SendGrid | 100/day | $19.95/mo for 50K | Per send |
| Mailgun | Trial only | $15/mo for 10K | Per send |
| MailerSend | 3,000/mo | $24/mo | Per send |
| Loops | 1,000 contacts | $49/mo | Per contact |
| Brevo | 300/day | $9/mo | Per send |
| AgentMail | Limited free | Usage-based | Per inbox and usage |
Compliance and deliverability controls
Authentication and compliance
Checked 3 September 2026| Provider | SPF / DKIM setup | DMARC guidance | Dedicated IP | Stream separation |
|---|---|---|---|---|
| Nitrosend Streams split by default | Guided | Yes | $50/IP/mo | Yes |
| Postmark | Guided | Yes | Available | Message Streams |
| Resend | Guided | Yes | $30/mo | Partial |
| Amazon SES | Manual | Docs only | Available | Configuration sets |
| SendGrid | Guided | Yes | Available | Separate products |
| Mailgun | Guided | Yes | Available | Yes |
Every provider in this table supports SPF and DKIM. None of them can fix an unauthenticated domain for you, and none can rescue a list that was never consent-collected. The authentication guide covers the three records, and warming a domain covers the ramp.
How to use this table
Pick the two columns that are non-negotiable for you and eliminate on those first, rather than scoring everything. In practice that is usually:
- Need inbound? Mailgun, Postmark, AgentMail. Nitrosend is out.
- Need SMTP submission? Everyone except Nitrosend, Loops and AgentMail.
- Need transactional and marketing in one account? Nitrosend, Loops, Brevo.
- Need an agent to operate the account? Nitrosend, then AgentMail for inbox work.
- Need the lowest unit cost? Amazon SES, with something on top.
- Need a first-party SDK in Ruby, Go or .NET? Postmark, SendGrid, Resend.
Then rank the survivors on the weighted list.
FAQ
Which email API has the best documentation?
Resend, followed by Postmark. Both keep docs in step with the API and provide runnable examples in several languages.
Which email API has the best deliverability?
Postmark for transactional-only sending, on the strength of Message Streams and a long placement record. Deliverability is mostly a function of your domain authentication, list quality and sending pattern rather than your vendor.
Which email API has the best webhook support?
Mailgun and Postmark have the most mature event surfaces. Every provider in this table signs webhooks, so check retry behaviour and replay, which is where they differ.
Which email API has the best SLA?
Contractual SLAs generally start at enterprise tiers. Nitrosend publishes 99.9% on Enterprise at $300 a month, and SendGrid and Amazon SES offer enterprise agreements. Below enterprise, most providers publish a status page rather than a guarantee.
Which email API is cheapest?
Amazon SES at $0.10 per 1,000, by a wide margin, if you can absorb the operational work. Bundled platforms cost more because they include the layer SES omits.