What are common warmup mistakes?

Warmup is one of those things that looks simple until you're in the middle of it and suddenly your open rates are tanking and you're not sure what went wrong. Most warmup mistakes fall into a few predictable patterns, and the good news is they're all avoidable once you know what to watch for.

Ramping up too fast. This is the most common one. You send 500 emails on day one, things look fine, so you jump to 5,000 on day three. Mailbox providers notice sudden volume spikes and treat them as a red flag. A safe warmup schedule usually doubles volume every few days, not every few hours. Patience here is not optional.

Starting with the wrong people. Your warmup audience matters more than your volume. Sending to unengaged contacts, old lists, or anyone you haven't had recent two-way contact with is asking for trouble. Complaints and low opens early in warmup send a terrible first impression to Gmail and Outlook before you've built any reputation at all. Start with your most engaged subscribers, the ones who open reliably and have heard from you recently.

Broken authentication before you even start. If your SPF, DKIM, or DMARC isn't set up correctly before warmup begins, you're building reputation on a shaky foundation. DNS problems discovered mid-warmup can reset your progress entirely. Check your authentication setup first, before a single warmup email goes out.

Ignoring the signals. Warmup is not a "set and forget" process. You need to watch your metrics every day. Soft bounces climbing? Spam complaint rates rising above 0.1%? Deliverability to one provider dropping while others look fine? These are warning signs. The mistake isn't seeing problems, it's continuing to send anyway and hoping things improve on their own. They don't.

Irregular sending. Mailbox providers want to see consistent, predictable behavior. If you send nothing for four days and then blast a big volume, you've undone some of the trust you built. Gaps and erratic volume patterns look suspicious. Even a small daily send is better than silence followed by a spike.

Thinking warmup is just about volume. Volume is one part of it, but your content, engagement rate, and sender behavior all matter too. Sending a wall of promotional text to a cold list and hitting decent delivery numbers isn't a win if nobody opens it. Mailbox providers are watching what recipients do with your emails, not just whether they arrive.

If you're mid-warmup and things feel off, check your metrics closely before pushing forward. Our Blocklist Checker is a good first stop to see if any damage has already landed on your domain. And if you're stuck on what to do next, the SOS hotline is free.