Why a campaign stops partway through
You sent a campaign to your whole list, and the numbers say only part of it went out. Some contacts got the email, the rest did not, and you want to know why it stopped and how to reach the others without sending anyone a second copy. A campaign that stopped partway through sending is one where delivery halted after some recipients and before the last, so the sent count sits below the number of people the campaign targeted.
The quick answer is that a partial send almost always has an ordinary cause: a daily recipient allowance ran out, the send was held for review, someone paused or canceled it, or the sending provider started rejecting messages over its own limits. The gap can be large. A stopped send can leave a large part of a list unreached. Put two numbers side by side, the recipients the campaign targeted and the messages that actually went out, then check the causes below in order.
The part that matters most is how you finish. A paused campaign can pick up where it left off. A canceled one cannot. The email marketing guides cover the wider program, and the guide to what an email campaign is and how to run one covers the send from the start.
What stops a campaign mid-send?
Check these four causes in order. The first two are limits and holds working as designed. None of the four means the email itself was wrong.
Four causes and the first check for each
| Cause | What it looks like | First check |
|---|---|---|
| Recipient allowance reached | Sent count near your rolling 24-hour allowance, which starts at 100 on the free plan | nitro_manage_billing |
| Held for review | A newer account sending to more than ten recipients, or an account that has added over 20,000 contacts | nitro_get_status |
| Paused or canceled | Delivery stopped at a point someone chose | nitro_query |
| Provider rejections | Recipient-limit errors from your own sending provider | nitro_configure_providers |
Each cause, and how to fix it, is covered below.
Paused and canceled are not the same
A paused campaign keeps its place. Resuming it carries on delivering to the contacts who have not received it yet. To resume a paused campaign in Nitrosend, use nitro_control_delivery.
A canceled campaign is finished. It cannot be resumed to deliver the emails it never sent, however many are left. Re-sending a canceled campaign to the full list emails everyone who already got it.
How to fix each cause
Recipient allowance reached
Every plan caps how many people commercial email can reach in a window. On the Nitrosend free plan, commercial email starts at 100 recipients per rolling 24 hours, and the daily allowance depends on your plan and sender standing, so a campaign to a larger list will not reach every contact inside one day. Hitting that cap is a limit on volume, not a flag on your Nitrosend account, and nothing about the email needs to change.
Read the current plan and allowance with nitro_manage_billing, the MCP tool for billing and plans. If the list is larger than the allowance, either let the send continue across days or move to a plan with more headroom. nitro_manage_billing can create a subscription checkout link for someone on the account to approve. Sending to a smaller, more engaged segment first is often the better choice anyway, as the guide to email marketing for small business explains. The guide to mass email marketing covers sending to large lists.
Held for review
A safety check can hold a send for review before it goes out in full, for example from a newer account sending to more than ten recipients, or from an account that has added over 20,000 contacts. From the outside it looks like a stopped campaign, though nothing has failed.
Check nitro_get_status for account readiness, sender identity and any recommendations. Finish whatever setup it flags, and give the review time before starting a second send, since a duplicate campaign makes the hold harder to sort out, not easier.
Paused or canceled
A teammate, a scheduled change, or an agent acting on an instruction may have stopped delivery. Look up the campaign with nitro_query, which can query any Nitrosend entity, and confirm which state it is in. If it is paused and the reason for pausing has passed, resume it with nitro_control_delivery. If it is canceled, go to the next section.
Provider rejections
If you send through your own email provider, its account limits apply on top of your plan. When a provider hits a recipient limit it rejects further messages, and the rest of the campaign fails even though the first part went out cleanly.
Check the provider connection with nitro_configure_providers, which configures your own provider credentials and reports provider status. Raise the limit with the provider, or wait for its window to reset, before sending to the contacts who missed out. Sending again into the same limit just produces the same rejections.
Finishing the send without doubling up
The clean way to reach people who did not get an email from a stopped campaign is to run a new campaign to just those contacts. In practice that takes four steps.
- Look up the stopped campaign and its recipients with
nitro_query, so you know who received it. - Build a segment or list of the contacts who did not, with
nitro_manage_audience. - Create a new campaign with the original content, aimed only at that segment, in the same place the original was built. Run it through
nitro_review_delivery, then send yourself one real copy withnitro_send_test_messageto confirm it renders. - Approve delivery with
nitro_control_delivery, after confirming that the allowance, review or provider limit behind the first stop has cleared.
If the email mentions a date, a stock level or an offer that has since moved, update it in the new campaign. The contacts reading it a day late should not get a stale promotional email. For more on how campaign types differ in timing, see the guide to types of email marketing.
What to do next
- Compare targeted recipients with messages sent, so you know the size of the gap.
- Check the four causes in order, and stop at the first one that fits.
- If the campaign is paused, fix the cause and resume it. If it is canceled, send a new campaign to the missed contacts only.
- Before the next large send, check the plan allowance against the list size.
An agent with these tools can run the checks and build the follow-up campaign from Claude, Cursor or any other MCP client, which the guides to AI email marketing and API email marketing cover. Billing changes still need approval from someone on the account. To script the check instead, start with the Nitrosend CLI, the guide to Python email automation, or the full list of email API language guides.
Go deeper
Common questions
The usual reasons, in order of likelihood, are a daily recipient allowance that ran out, a send held for review, a campaign that someone paused or canceled, and a sending provider that started rejecting messages over its own limits. Compare how many recipients the campaign targeted with how many messages actually went out, then work through those four in order.
No. A paused campaign can be resumed, but a canceled campaign cannot be restarted to deliver the emails it never sent, even when only the last 1,322 are left. To reach the people it missed, build a segment of the contacts who did not receive it and send a new campaign to that segment alone.
Finishing takes four steps. Find out exactly who received the first send, build a segment of the contacts who did not, send a new campaign to that segment alone, and approve it only after the limit behind the first stop has cleared. Never re-send the original to the full list, because everyone who already received it gets a second copy.
No. A plan allowance stopping a send is a cap on volume, not a flag on your Nitrosend account. On the free plan, commercial email starts at 100 recipients per rolling 24 hours, so a larger list finishes across more than one day or needs a larger allowance. Nothing about the email itself needs to change.
On the free plan, commercial email starts at 100 recipients per rolling 24 hours, and the daily allowance depends on your plan and sender standing. A campaign to a larger list will not reach every contact inside one day on that allowance.