How to warm up an inbox with the Warmup Engine

Mailbox providers judge a sender by its history. A brand-new inbox that suddenly sends hundreds of cold emails looks exactly like a spammer. Warmup fixes that by sending a small, steadily growing volume of natural-looking emails, so Gmail and Outlook learn that the address is a real, trusted sender.

Start warmup

1. Open Warmup Engine from the sidebar.
2. Pick the account and choose Start warmup.
3. Review the settings (the defaults below suit most new inboxes) and confirm.
4. Leave it running. The Warmup Engine page shows each inbox's ramp day, today's sends against its target, the warmup score, replies received and a volume chart.

Default settings

• Starts at 2 warmup emails a day.
• Adds 1 email a day as the ramp progresses.
• Levels off at 40 warmup emails a day.
• 21-day ramp period.
• Sends Monday to Friday, between 08:00 and 20:00 in the timezone you choose.
• Daily counters reset automatically at midnight UTC.
• Warmup and campaigns share one limit of 50 emails a day per inbox, so a high warmup volume leaves less room for campaign sends.

Reading the warmup score

The warmup score rises by 1 for every warmup email an inbox sends, up to 100, so it shows how much sending history the inbox has built rather than how recipients engaged. 80 or more counts as ready for cold campaigns. If the score stops climbing while warmup is on, emails aren't going out, so check the inbox connection and its sending window. Warmup builds history but can't fix authentication, so run a Spam Score check and confirm SPF, DKIM and DMARC are in place.

When is an inbox ready?

Wait until the ramp completes (about three weeks for a new inbox) before sending cold campaigns at full volume, then increase campaign sends gradually. Keep warmup switched on while the account is in use: ongoing positive engagement offsets the lower reply rates that cold email naturally produces.

Next: check your spam score