Warmup is not a trick. Here's what it actually does.

Inbox providers trust mailboxes that behave like people. Warmup teaches a new mailbox to behave like one, and it can't fix a bad list.

A brand-new mailbox has no history. Providers don't know whether it belongs to a person or a spammer, so they watch closely. Send 500 cold emails from it on day one and the answer they reach is obvious.

What warmup does

Warmup builds history slowly. The mailbox sends a small number of emails to other mailboxes in a warmup network, which open them, reply to them, and move them out of spam if they land there. Volume rises a little each day. To a provider, the mailbox starts to look like a person having normal conversations.

• Start low, around 5 to 10 warmup emails a day, and ramp over two to four weeks.
• Keep warmup running at a low level after you start campaigns. Reputation fades if the only mail you send is cold.
• Warm the domain too. A new domain needs the same patience as a new mailbox.

What warmup can't do

Warmup doesn't make bad sending good. If your list has invalid addresses, your bounce rate climbs and reputation falls, however warm the mailbox. If your copy reads like spam, recipients will mark it as spam. Verify every list, keep each mailbox's daily volume modest, and write emails a person would answer.

How Inboxed handles it

Warmup is free in Inboxed for every connected mailbox. Warmup emails carry a reference so the receiving mailbox can recognise them: they are opened, sometimes answered, moved out of spam if they land there, and never shown in your team inbox. Where they land gives each mailbox a health score.

Try it

Warmup, verification and the team inbox are free. Start free; you only pay $1 per 1,000 emails that send.