Warmup · 5 min read
Set up email warmup
Switch on warmup, understand the ramp and read the results so new mailboxes are ready for campaigns.
· Mailnitrix team
Warmup builds a mailbox's sending reputation by having your connected mailboxes email each other, open those emails, rescue them from spam and reply. This guide walks through switching it on and reading the results.
Before you start
- Connect at least two mailboxes. Four or more works best, because each mailbox needs partners to send to and hear from.
- Each mailbox needs IMAP access. Gmail and Outlook mailboxes connected as described in the Gmail and Outlook guides already have it.
Step 1: Switch warmup on
- Open Warmup in Mailnitrix. You'll see every mailbox in your account.
- Turn warmup on for each mailbox you want to warm up.
Warmup starts with the next planning cycle. The first emails go out within the mailbox's sending window, 8:00 to 19:00 in its time zone by default.
Step 2: Understand the ramp
| What | Default |
|---|---|
| First day | 3 warmup emails |
| Daily increase | About 2 more each day |
| Maximum | 30 a day |
| Weekends | Half volume |
| Replies | About a third of received warmup emails get a reply |
If fewer than 70% of a mailbox's warmup emails reach the inbox over three days, its ramp holds steady until placement recovers.
On Turbo and above you can change these settings per mailbox.
Step 3: Let the campaign ramp work
New mailboxes don't send campaign emails during their first two weeks of warmup. From day 14 they can send 10 campaign emails a day, and that cap rises by 5 each day until it reaches the mailbox's daily limit. You'll see each mailbox's campaign cap today on the warmup page.
Mailboxes that already send regularly, 50 or more emails in the last 14 days, skip this ramp automatically.
Step 4: Read the results
For each mailbox, the warmup page shows:
- Inbox rate: the share of warmup emails that landed in the inbox over the last 7 days. Aim for 90% or higher before sending campaigns at full volume.
- Saved from spam: warmup emails found in spam and moved back to the inbox. A few early on is normal; a steady stream means the mailbox or its domain needs attention.
- Replies: how many warmup threads got a reply.
- History: a 30-day chart of volume and placement.
Troubleshooting
- Nothing is being sent: check that at least two mailboxes have warmup on, and that the mailbox is active, not in a cooldown.
- "IMAP" or login errors: the mailbox's app password was revoked, or IMAP is blocked by a Workspace or Microsoft 365 admin. Reconnect the mailbox.
- Low inbox rate that doesn't improve: check SPF, DKIM and DMARC for the domain, and lower the mailbox's campaign volume while warmup continues.
Keep it running
Don't switch warmup off when campaigns start. It keeps running alongside them at a steady level and continues to build reputation. Warmup emails never count toward your plan's monthly emails.