How to warm up your sending addresses

A new cold email address on a new domain starts at 5 emails a day and climbs over 14 sending days, writing only to confirmed mailboxes, once its DKIM, SPF and DMARC records are in place.

Updated 2026-10-30

Mail services such as Gmail and Outlook are wary of a domain they have never seen. If a brand-new domain sends 30 cold emails on its first day, many of them can land in spam, and the domain can be marked for a long time. So Otto warms up each new sending address: it sends very few emails at first and a few more each day.

There is nothing to switch on. It happens by itself for every cold email address on a domain Otto has not sent from before.

Which addresses warm up

An address on a domain Otto has never sent cold email from, such as a look-alike domain you just bought (getyourcompany.com), warms up.
Once one address on a domain has finished its warm-up, a new address on the same domain starts on the normal ramp instead: the domain already has a good name with mail services.
Addresses that were already sending before warm-ups began do not warm up again.

How it goes

Day 1: 5 emails.
Each day it sends on, a few more: 7, 9, 10, 12 and so on, up to 28 on day 14. A day it sends nothing (a weekend, or nobody it may write to yet) does not count.
After 14 sending days the address is Ready. It moves on to the normal ramp: 30 a day, never above 50 a day for its first two weeks, then about a tenth more after each full day while bounces and spam reports stay low.

Who it writes to while it warms up

While an address warms up, it sends only first emails, and only to confirmed mailboxes (addresses printed on the business's own website, or that passed the paid address check) and to your own imported list, where the address's domain takes mail. It does not write to:

follow-ups, which wait until the address is ready;
catch-alls, where the business's domain takes every address so this one cannot be proved;
guessed addresses that were not checked.

Nobody is dropped. They wait, and are written to once the address is ready.

It waits for your domain's records

The warm-up does not start until the domain passes all three email checks:

DKIM: the records Otto shows when you add the domain. The domain shows Verified once they are seen.
SPF: a record that says Amazon may send for your domain.
DMARC: a record that tells mail services what to do with mail that fails the other checks.

If one is missing, the address shows Not started under Growth → Outreach → Cold campaigns → Domains and mailboxes, with the record it is missing beside it. The SPF and DMARC records to add are shown under Sending domains. Add them where your domain's records are kept (the company you bought it from). When you bought the domain through Otto, its DKIM and DMARC records were added for you, but its SPF record was not: add that one yourself. If Otto could not read your domain's records just then, it says so and checks again.

See where it is

Under Domains and mailboxes, the Mailboxes list shows each address's warm-up:

Warming up · day 4 of 14 · 10 a day today
Ready
Not started, with the reason beside it.

A practice run plays the warm-up out day by day too, with nothing sent.

Inbox placement tests

An inbox placement test sends one email from an address to test mailboxes at Gmail, Outlook and Yahoo and shows what share landed in the inbox and what share in spam. Press Test inbox placement beside an address, then Check result a few minutes later.

This works only when inbox placement tests are switched on for your Otto server. Until then the button is off and the reason is shown beside it. Otto never shows a made-up result, and a test with nothing counted yet says "No result yet", not that all is well.

Why not a warm-up network?

Some tools warm up an address by trading emails with thousands of other people's inboxes. Your cold email addresses are addresses Otto sends from, not inboxes, so those networks cannot reach them. The warm-up here is simply how slowly Otto itself sends at first.