Microsoft weights sender reputation via SNDS and JMRP, and rejects unauthenticated bulk mail to consumer Outlook.com addresses.
What email list hygiene is#
List hygiene is the ongoing removal of invalid, inactive, and risky addresses from a mailing list, plus verification of new addresses at the point of capture.
Why it matters#
Bounces, spam traps, and disengaged recipients are the three fastest ways to damage reputation, and all three are prevented by hygiene.
Setting up email list hygiene for Outlook and Microsoft 365#
- Verify new signups in real time with an API and use double opt-in for marketing lists.
- Suppress hard bounces immediately and soft bounces after 3 consecutive failures.
- Run a re-engagement campaign at 90 days of inactivity and sunset at 180.
- Remove role accounts (info@, sales@) and disposable domains from marketing lists.
- Audit the list quarterly with a bulk verification service.
How Outlook and Microsoft 365 reports results#
Open a delivered test message in Outlook and Microsoft 365 and view the original or headers. Look for Authentication-Results and any provider-specific verdict headers. Use the provider's sender dashboard for aggregate reputation.
Common mistakes#
- Importing old exports without verification.
- Keeping unengaged contacts because the list size looks good in reports.
Frequently asked questions#
What is a spam trap?
An address that never opted in, maintained by providers and blocklists to catch senders with poor acquisition practices. Hitting one can blocklist your IP or domain.
What bounce rate is acceptable?
Under 2% hard bounces. Above 5% typically triggers ESP account reviews.
Does Outlook and Microsoft 365 require email list hygiene?
Microsoft weights sender reputation via SNDS and JMRP, and rejects unauthenticated bulk mail to consumer Outlook.com addresses. Treat email list hygiene as required for any meaningful volume.