How to warm up a new sending domain

A new sending domain has no reputation. That is not neutral. Mailbox providers have seen millions of new domains appear and send a burst of mail before disappearing, and they treat yours the same way until it behaves differently.

Warming up means earning volume gradually, so the provider sees good engagement before it sees scale.

Before you send anything

Get the basics right first, because a warm-up on broken authentication teaches the provider the wrong thing:

• SPF and DKIM both passing, and a DMARC record, at least p=none.
• Your From: domain aligned with the domain that passes SPF or DKIM.
• A clean list. Remove hard bounces and anyone who has not engaged in months before you start.

A ramp that works

Start with the recipients most likely to open and least likely to complain: recent sign-ups, active customers, people who asked for the mail. Then grow the share of your list in steps, and only move up when the previous step went well.

A common shape is to double each step: 5% of your list, then 10%, 20%, 40%, then all of it. Leave a day or more between steps so the providers’ feedback has time to arrive. For a large list, the early steps may need splitting across several days.

Transactional mail warms up a domain too. Password resets and receipts are mail people expect and open, and they build reputation steadily. That is one reason to keep them on the same domain as your newsletter, on a separate stream, rather than hide your marketing on a domain that has never sent anything useful.

Signals that mean stop

Pause the ramp and hold your volume where it is if you see any of these:

• Deferrals rising at one provider. A 4.7.x response is the provider asking you to slow down, usually with a reason. Respect it, and resume when it clears.
• Bounces above about 2%. Your list is older than you thought. Clean it before you go further.
• Complaints approaching 0.1%. Gmail treats 0.3% as the ceiling, so 0.1% means you are sending to people who do not expect you.
• Open rates falling step on step. You may have run out of engaged recipients and started on the cold end of the list.

Holding volume is not a failure. Pushing through warning signals is how a two-week warm-up becomes a two-month recovery.

How Outsend handles it

Outsend campaigns can step a new sending identity up over days, 5%, 10%, 20%, 40%, then the full list, pausing automatically between steps. Reputation is scored per domain and per workspace, so one domain’s bad week does not spend another’s reputation. Every deferral keeps the provider’s own words, so you can see why a step paused rather than guess. The campaigns page has the detail.