How to warm up a new email domain for cold outreach (a 4-week schedule)

A new domain has no reputation. Not a bad one — none. Every receiving server that sees mail from it for the first time has nothing to go on except the message and the sending pattern, and cold email is the one kind of message where that first impression is stacked against you. Warming up is how you give the domain a history before it needs one.

This is the schedule we use for new outreach domains. It assumes lookalike domains dedicated to outreach, two or three mailboxes each, and a warmup network of real inboxes — the setup in the deliverability checklist.

Before day one: the domain

1. Register the outreach domains early. Domain age is a mild signal on its own; more importantly, a domain that has existed for months with a website and no spam history is boring, and boring is good. Buy them weeks or months before you need them if you can.
2. Put a real site on each. A one-page redirect to your main site is enough. A domain with no web presence and sudden outbound mail is a recognisable pattern.
3. Set up SPF, DKIM and DMARC before the first message of any kind leaves. Exact records here. DMARC at p=none is fine to start.
4. Create two or three mailboxes per domain, with real names and profile details, and send a handful of ordinary emails from each by hand — to colleagues, to yourself — so the first traffic the provider sees is human.
5. Connect them to warmup and let it run. In MailFleet, connect the mailboxes via CSV (Google mailboxes need an app password), turn warmup on in bulk, and set a daily ramp.

The four-week schedule

Two rules sit under the table:

• Never turn warmup off once a mailbox is "warm". A mailbox that only ever sends cold email and never receives replies looks exactly like what it is. Steady warmup at 20 a day keeps the engagement signals alive.
• The ramp is per mailbox. Adding a new mailbox to a warm domain still means a week of warmup-only for that mailbox; the domain's reputation helps, the mailbox's own is still zero.

MailFleet's defaults follow this: warmup at 20 a day with a 30-minute gap and a 30% reply rate, an optional daily ramp-up, new mailboxes capped at 30 sends a day with a 20-minute gap, and campaigns admitting 100 new leads a day.

What good warmup traffic looks like

Not every "warmup" is equal. The signals providers actually score are engagement, so the warmup has to produce engagement:

• Messages are opened by the receiving inbox.
• Messages that land in spam are moved to the inbox — this is the single most valuable signal, because it tells the provider its filter was wrong about you.
• A share of messages get replies, and the conversation continues.
• The counterpart inboxes are real, warmed mailboxes, not a pool of throwaway accounts that a provider can identify as a warmup ring.
• Volume varies day to day rather than hitting the same number every morning.

MailFleet's warmup does all five across every customer's connected mailboxes, tags each message with a workspace code word so it never appears as a reply, and randomises daily volume within a range you set. Details on the email warmup page.

Week 2 onward: what to watch

• Bounce rate per domain. Under 2% is healthy. Above that, stop adding new leads and verify the list; above 4% pause the domain. MailFleet's Deliverability page flags a domain at 4% bounced or 1.5% policy blocks.
• Policy blocks vs bad addresses. A "no such user" bounce is the list's fault; a "message rejected due to reputation" is the domain's. The second kind means slow down now.
• Reply rate. A campaign that got replies in week two and none in week three, with no copy change, has a placement problem, not a copy problem.
• Google Postmaster Tools for each domain: domain reputation and spam rate. Free, and the only view Gmail offers.
• Your own seed inboxes. Keep one Gmail, one Outlook and one Yahoo address on every list and look where the mail lands.

If placement slips

1. Halve cold volume on the affected mailboxes. Don't stop entirely — silence followed by a restart looks worse than steady low volume.
2. Keep warmup running; if anything, nudge the reply rate up.
3. Check nothing changed: DNS records, a new tool sending from the domain, a list from a new source.
4. Give it one to three weeks. Reputation recovers on the same timescale it was built.
5. If a domain drops to Postmaster "bad" and stays there, retire it from cold outreach. A fresh lookalike domain warmed properly is four weeks; a burned domain can take months.

How long does warmup take?

For a new mailbox on an established domain: about a week before the first cold sends and two to three weeks to full volume. For a brand-new domain: two weeks before the first cold sends and about four weeks to full volume, as in the table. Anyone promising "warmed in 48 hours" is describing a mailbox that will work for a few days.

FAQ

How long should I warm up a new domain before cold emailing?

About two weeks of warmup-only sending, then two more weeks ramping cold volume from 5–10 to 20–30 a day per mailbox. Roughly four weeks to normal operation.

Should I keep warmup on after the domain is warm?

Yes, permanently, at a steady level (MailFleet defaults to 20 a day). Reputation decays without engagement.

How many warmup emails per day?

10–20 in the first week, 20–30 thereafter. More is not better; a new mailbox sending 100 warmup emails a day is itself a bulk-sending pattern.

Can I warm up a domain without a tool?

Partly — sending real emails to colleagues who reply does the same thing at a small scale. A network makes it consistent and handles the spam-rescue signal, which is hard to do by hand.

Does warmup use my email credits?

Not in MailFleet. Warmup is free on every plan and never counts against credits or a mailbox's daily limit.