Warm-up service
A service whose network of mailboxes exchanges messages with yours, replies to some and moves any found in spam to the inbox, to generate engagement before real sending.
What it means
Vendors describe the mechanism openly. VoilaNorbert's help, for example, says its tool sends emails from your address to a set of addresses it manages, replies to a share of them to create a reply rate, and marks any that land in spam as not spam.
The engagement these tools create is simulated. M3AAWG's sender practices say artificial warming practices are not recommended and may be illegal, and its position on cold email lists attempts to artificially simulate subscriber engagement among practices that are not acceptable in any manner.
Warm-up of a real program means real mail to engaged recipients at gradually rising volume, as Google and AWS describe.
Related terms
On this site
Sources
What this definition rests on. The wording is ours; the facts are theirs.
- VoilaNorbert Help: How does the warm up tool work?docs.voilanorbert.com
- M3AAWG Sender Best Common Practices, version 4.0 (August 2026)m3aawg.org
- M3AAWG Position on Cold Email (November 2025)m3aawg.org
- Amazon SES: Warming up dedicated IP addressesdocs.aws.amazon.com
All 432 terms in the glossaryThe wiki: blocklists and bounce codes