Deliverability is a discipline, not a setting

Most "our emails go to spam" problems are not bugs. They are the predictable result of treating deliverability as a checkbox instead of a habit.

Reputation is earned at the rate of trust

Mailbox providers decide placement on signals they have watched over time: consistent volume, low complaints, real engagement. A new IP has no history, so it gets no benefit of the doubt. You have to give it one, slowly.

What warming actually is

Warming is sending small, then a little more, to your most engaged contacts first, over weeks, so providers learn that your mail is wanted before you ever send at scale. Skip it and the first big send teaches them the opposite.

• Start with the people who open and click
• Ramp volume on a schedule, not a whim
• Watch complaint and bounce rates like a dashboard, not a quarterly report

The signals providers watch

• Bounces: addresses that do not exist tell a provider you do not know your list
• Complaints: the strongest negative signal, and the hardest to recover from
• Engagement: opens, clicks, replies, and also deletions without reading
• Consistency: sudden jumps in volume look like a compromised account

Large providers have also made some of this explicit. Google and Yahoo published requirements for bulk senders in 2024: authenticated mail, easy one-click unsubscribe, and a spam complaint rate that stays low. Google's guidance is to stay under 0.1 percent and never reach 0.3 percent.

An example ramp

This is an illustration of the shape, not a prescription. Adjust it to your list size, your engagement, and what your provider dashboards show.

• Week 1: only the most engaged segment, in small daily batches
• Week 2: roughly double the volume if bounces and complaints stay flat
• Weeks 3 and 4: widen to recently active contacts, keep the daily rhythm
• Weeks 5 and 6: bring in the rest of the list in stages, least engaged last

The foundation: authentication

Before any warming plan matters, three records need to be right:

• SPF: lists which servers may send for your domain
• DKIM: signs each message so providers can verify it was not altered
• DMARC: tells providers what to do when SPF or DKIM fail, and sends you reports

Without them, even a perfect ramp starts with a handicap.

Common mistakes

• Scaling before there is a clean engagement baseline
• Mailing old, unvalidated lists "just once"
• Changing sending domain, IP, and content all at the same time
• Looking at the numbers only after a send has already gone wrong

The quiet work behind the loud numbers

No campaign metric survives a spam folder. Deliverability is the unglamorous half of every result, and the half most teams notice only once it is gone.