Microsoft weights sender reputation via SNDS and JMRP, and rejects unauthenticated bulk mail to consumer Outlook.com addresses.
What dedicated IP addresses are#
A dedicated IP is used only by your mail; a shared IP pool is used by many senders on the same platform. Dedicated IPs give control over reputation but require volume and warm-up; shared pools borrow the platform's reputation.
Why it matters#
Choosing wrong either exposes you to neighbors' behavior or leaves an IP too cold to build reputation.
Setting up dedicated IP addresses for Outlook and Microsoft 365#
- Estimate steady daily volume; below roughly 50,000 per day, shared pools usually perform better.
- If dedicated, warm up over 4 to 6 weeks and keep volume consistent.
- Separate transactional and marketing onto different IPs or pools.
- Monitor SNDS and Postmaster Tools per IP.
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#
- Buying a dedicated IP for a small list and letting it go cold.
- One dedicated IP for everything, so a promo blast delays receipts.
Frequently asked questions#
Do I need a dedicated IP for good deliverability?
No. Domain reputation dominates. Dedicated IPs are for high-volume senders who want isolation.
Does Outlook and Microsoft 365 require dedicated IP addresses?
Microsoft weights sender reputation via SNDS and JMRP, and rejects unauthenticated bulk mail to consumer Outlook.com addresses. Treat dedicated IP addresses as required for any meaningful volume.