Sending Volume and Warmup
New senders should build trust gradually instead of sending a large campaign right away.
Overview
Sending volume is the amount of mail you send over a period of time. Warmup means increasing that volume gradually so inbox providers can see a healthy sending pattern before you send larger campaigns.
A new sender has little sending history. Sending a large campaign right away can look risky to inbox providers, especially if the list is old or subscribers are not engaged. Read Sender Reputation and Spam Rate if you are preparing a new domain or email delivery service.
Warmup is not only about send counts. Warmup works best when you send wanted email first. A small send to engaged subscribers creates a better signal than a large send to people who forgot they subscribed.
Volume spikes can cause throttling, deferrals, or reputation drops. If an email delivery service or mailbox server slows your mail, read SMTP Errors, Deferrals, and Throttling before you retry aggressively.
To reduce risk, start with subscribers who are most likely to want the email. These subscribers may be recent signups, active customers, or people who clicked a recent campaign. Then increase volume only while results stay healthy.
What to Do
- Confirm SPF, DKIM, DMARC, and alignment before you warm up a sender.
- Start with subscribers who recently signed up, opened, clicked, purchased, or replied.
- Avoid old imports, inactive subscribers, and uncertain sources during early sends.
- Send at a steady pace instead of sending one large burst.
- After each step, review bounces, complaints, unsubscribes, opens, clicks, and replies.
- Increase volume only when those results stay healthy.
- If throttling, deferrals, bounces, or complaints increase, pause volume growth and fix the cause.
What to Check
- Start with recent and engaged subscribers when a domain, email delivery service, or sender identity is new.
- Do not use an old imported list as the first campaign from a new connection.
- Watch Bounces, Spam Complaints, unsubscribes, and replies closely after early sends.
- Pause sending growth and fix the cause if early sends show high bounce or complaint rates.
- Keep launch-day campaigns simple until the sender proves it can deliver well.
- Warmup does not repair a bad list. Warmup only gives a good sender a gradual start.
- Email delivery service warmup tools can help, but they do not replace permission and list quality.
Fix Common Issues
Risky Address Segment
A bulk email list checker found risky or unknown rows, such as role inboxes, disposable domains, typo risks, or DNS uncertainty.
- Do not include risky rows in the first broad campaign.
- Export the clean rows separately and send to those subscribers first.
- Review risky rows manually when possible.
- If you keep some risky rows, send to them in a smaller segment after the sender has healthy results.
- Watch bounces and complaints closely before you increase volume.
Note
Warmup is not a trick. Warmup is a controlled way to prove that subscribers want the mail before you send more of it.