Microsoft Warns Office 365 Users to Authenticate Emails or Risk Being Marked as Spam by Gmail

Microsoft warned Office 365 email senders to authenticate outbound messages to avoid being flagged as spam by Gmail due to new anti-spam rules.

Failure to follow email authentication standards could lead to emails being rejected or marked as spam by providers like Gmail.

Microsoft advised not using Office 365 for sending bulk emails, as it may trigger outbound spam controls and delivery pooling. Use own servers or third-party providers instead.

For bulk emails through Office 365, follow guidance around sending limits, using separate subdomains, and configuring authentication.

Google will require senders of over 5,000 daily emails to Gmail users to implement authentication and unsubscribe options by February 2024 to combat spam.