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Short answer
Yes. Keep warmup running for as long as the mailbox sends cold email. It keeps a steady flow of emails that are opened and replied to alongside your cold volume, and its inbox and spam rate warn you early when a mailbox or domain starts to slip. Keep warmup volume steady and change it only in small steps.
Why keep it on
Warmup doesn't end when cold email starts. Two reasons to keep it running:
It balances your traffic. Cold email gets few opens and replies. Warmup adds a steady stream of emails that are opened, replied to and rescued from spam, from the same mailbox, every day.
It is your early warning. The warmup inbox and spam rate move before replies do. A mailbox or domain whose warmup emails start landing in spam is losing trust with the provider, and you see it within days.
Stopping warmup after the first two weeks removes both. The mailbox then sends only cold email, with no signal until replies fall.
Keep it steady
Google's sender guidelines ask senders to "Send email at a consistent rate. Avoid sending email in bursts," and warn that "immediately doubling previously sent volumes suddenly could result in rate limiting or reputation drops." That applies to warmup too:
Keep warmup volume at a stable daily level.
If you change it, change it in small steps over several days.
Don't raise warmup sharply to "rescue" a mailbox. Abrupt jumps in warmup volume make placement worse.
Keep the default warmup topic. Don't switch warmup content to match your offer.
What warmup metrics tell you, and what they don't
Signal | What it means |
|---|---|
Warmup inbox rate stable | No early warning. It does not prove cold placement |
Warmup spam rate rising | The provider trusts the mailbox, domain or sending IPs less. Act on it |
Warmup rate falls on one domain only | That domain is the likely problem |
Warmup rate falls on all domains on the same IPs | The sending IPs are the likely problem |
A high warmup score does not prove your cold emails land in the inbox. Warmup partners have a history with your mailbox; your prospects don't. Use placement tests and replies to judge cold email. See placement tests.
Check that it is actually running
"Connected" in a sending tool only means the tool can log in. Warmup can be stopped, disabled after an import, or never started because DNS wasn't ready. Confirm that warmup emails are being sent and received for every mailbox, especially after moving mailboxes between tools.
Free guide19 min read
Send 100,000 cold emails a month
Domains and mailboxes you need, DNS, warmup, lists, copy and follow-ups, with a launch checklist, sent to your inbox.
Keep warmup out of your real inbox
If warmup emails show up where you read replies, check forwarding rules and warmup filters. Forward cold-mailbox mail only to internal mailboxes and keep it out of your main company inbox.
What we recommend at Outreach2day
Warmup is required. Warm up for at least 14 days before cold email, start low from day 14, reach full volume around day 21, and keep warmup running while you send. Warmup is included for as long as you keep the mailbox, and each mailbox shows its warmup inbox, spam and bounce rate.
Sources
- Google: Email sender guidelines: support.google.com/a/answer/81126
Related answers
- How Long Should I Warm Up a New Mailbox Before Cold Email?Warmup
- My Warmup Inbox Rate Dropped. What Does It Mean?Warmup
- How Many Cold Emails Should One Mailbox Send per Day?Volume and setup
- Are Inbox Placement Tests Reliable for Cold Email?Warmup
In depth on the blog
- Email Warmup Service: What It Does and Costs5 min read
- Best Email Warmup Tools: 10 Options Compared16 min read
