IP warming is the process of gradually increasing the number of emails sent from a new dedicated IP address, so that mailbox providers such as Gmail and Outlook can build up a picture of it before it carries your full volume. A new IP has no history, and a sudden flood of mail from an unknown source looks exactly like spam.
How IP warming works
Every server that sends email does so from an IP address. Mailbox providers keep a record of how mail from each address behaves: how many recipients exist, how many complain, how many engage. A brand-new dedicated IP has no record, so providers treat it cautiously, slowing it down or filtering it to spam if it suddenly sends a lot.
Warming gives them evidence in small doses. A typical schedule starts with a few hundred or a few thousand emails a day, sent only to your most engaged subscribers, and increases the daily volume in steps, often roughly doubling every few days, while you watch for warning signs. Spreading the volume across different providers helps, because each one judges separately. Depending on how much you send, reaching full volume usually takes several weeks.
The warning signs are deferrals (temporary “try again later” responses, common from Microsoft during warming), rising bounces or complaints, and falling inbox placement. If they appear, hold the volume steady or step back before continuing.
Most small businesses never need this. If you send through a shared IP, which is the default on most email platforms, the platform keeps that pool warm with many customers’ mail. You do, however, still have a domain reputation to look after, and a new sending domain benefits from a similar gentle start, known as domain warming.
Why it matters
A dedicated IP gives you a reputation that is yours alone, which helps large senders who do everything well and no longer want to share a pool with others. It does nothing for a small or irregular sender: an IP that sends a few thousand emails once a month never builds a steady record, and can perform worse than a well-managed shared pool.
Timing matters for UK retailers. Moving to a new dedicated IP or a new platform in October leaves little time to warm before Black Friday and Christmas, when volumes peak and mistakes cost the most. A rushed warm-up can damage your sender reputation at the worst moment of the year.
Common mistakes
- Paying for a dedicated IP at a volume too low to keep it warm.
- Warming with an old or unengaged list, which teaches providers the wrong lesson.
- Jumping to a full send partway through the schedule because a sale is starting.
- Pausing for weeks and then resuming at full volume as if nothing had changed.
- Ignoring deferrals and pushing more mail into a provider that is already slowing you down.
How to act on it
First, ask your email platform whether a dedicated IP makes sense at your volume; the honest answer for most small businesses is no. If it does, use the platform’s recommended schedule, start with the subscribers who clicked or bought most recently, and plan the move well away from your busiest season.
Check that authentication is in place before the first email, monitor Google Postmaster Tools and your bounce and complaint figures daily, and test inbox placement as volume grows. Bigger decisions, such as whether to change platforms at all, are best made as part of a digital marketing strategy rather than in a hurry before a campaign.