Mailbox warmup
Mailbox warmup is the practice of gradually increasing a new email account's sending volume while generating positive engagement (opens, replies, moving mail out of spam) so mailbox providers build trust in the sender before real campaigns ramp up.
How it works
An automated network exchanges low-volume, high-engagement messages from your mailbox for ~2–4 weeks, then volume scales up as reputation builds.
Why it matters
Sending cold volume from a brand-new mailbox is the fastest way to land in spam. Warmup establishes the engagement history providers look for.
How Autocloz handles it
Autocloz includes a 21-day warmup ramp and adaptive daily ceilings, so mailboxes (and other channels) scale only as fast as their reputation allows.
FAQ
How long should mailbox warmup take?
Plan for about three weeks before sending meaningful cold volume, ramping daily sends gradually rather than spiking.
Related terms
Sender reputation is the trust score mailbox providers assign to your sending domain and IP based on how recipients react to your mail — opens, replies, spam complaints, bounces and spam-trap hits. A high reputation lands you in the inbox; a low one routes you to spam or blocks you.
Inbox placement rate (IPR) is the percentage of delivered emails that actually land in the primary inbox rather than the spam/junk folder or a tab like Promotions. Unlike 'delivered' (which only means accepted by the server), IPR measures whether a human is likely to see the message.
Domain reputation is the trust score mailbox providers assign to your sending domain based on its authentication, sending history, engagement and complaint signals. Unlike IP reputation, it follows the domain wherever it sends, which is why it has become the dominant reputation signal as senders share pooled IPs.
IP warmup is the process of gradually increasing sending volume from a new or dormant dedicated IP address while maintaining high engagement, so mailbox providers build trust in that IP before it sends full volume. Sending large volume from a cold IP triggers throttling or spam-foldering because providers have no history to trust.