Warming mailboxes without wasting three weeks

A new mailbox has no sending history, so providers have nothing to score it on. Warm-up exists to build that history with the kind of engagement signals that predict wanted mail: opens, replies, and messages moved out of spam.

Ramp volume rather than time. Ten to fifteen sends on day one, then a gradual daily increase, gets you further than sitting idle for two weeks and then opening the taps.

Reply rate matters more than open rate. A small number of genuine conversations does more for a young domain than hundreds of untouched sends.

Keep content stable during warm-up. Changing links, tracking domains or signature blocks mid-ramp muddies the signal you are trying to build.

Monitor placement per mailbox, not per campaign. One misbehaving identity on a shared domain drags the rest down long before your aggregate numbers show it.