What is email warm-up?
Email warm-up is building a new domain's or mailbox's sending volume slowly, with recipients who engage, before any campaign. New domains start with no reputation, and a domain that sends a lot in its first weeks looks like the throwaway domains spammers buy in bulk. Warm-up gives the domain a history before it has to carry volume.
Warm-up · Also: Email warm-up
Why do new domains need warm-up?
Because reputation is built on history, and a new domain has none. Spamhaus notes that "for the first 30 days after initial registration, most companies specializing in threat intelligence will flag a newly registered domain" and watch it for mass sending. Its advice is direct: "Don't send a bulk email run with your newly acquired domain name."
How does warm-up work?
- Authenticate first. SPF, DKIM and DMARC in place before the first email.
- Start with people who engage. Spamhaus recommends "a set of highly engaged recipients for the initial mailings."
- Raise volume step by step. Slowly, watching replies and bounces.
- Show who owns the domain. Do not hide it behind privacy masking, and connect it visibly to your brand.
Do new Microsoft tenants have limits too?
Yes. emailexpert reports that from September 14, 2026, Microsoft is rolling out lower limits for new Exchange Online tenants: 10% of the standard external-recipient quota for tenants less than 31 days old, and 25% from day 31 to day 60. The limit covers the whole tenant, not one mailbox, so cold email from your main tenant can hold up ordinary mail.
Do you need warm-up with Dylan?
No. Dylan writes from his own warmed domains and mailboxes, with a separate slice for each client, and your domain never sends a cold email. No DNS, no warm-up, nothing on your side to set up or burn.
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