Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Hello Elwood,
Outlook can temporarily restrict outgoing mail when its anti-spam system detects unusual sending activity, even when the messages are legitimate.
For Microsoft 365 subscribers, the published limits are 5,000 recipients per day, 500 recipients per message, and 1,000 recipients per day whom you have not emailed before; however, limits may vary according to account history. See more: Sending limits in Outlook.com.
Here are some suggestions you can try:
- Stop sending for 24 hours, then test by sending one simple email to a known contact. Repeated attempts or large recipient lists may prolong the restriction.
- Check your Sent folder, forwarding settings, inbox rules, and recent sign-in activity for anything unfamiliar.
- Change your password and enable two-step verification if necessary.
- Add regular recipients to Contacts and avoid sending many messages at once or placing large lists in BCC.
- Make sure that all your information (like phone number and alternate email address) is updated on your account.
- Make sure that you have updated your account's profile information (like Profile Name, Photo, Date of Birth, Gender, etc).
- Make sure the password which you have created is a combination of upper case/lower case letters, numbers and special characters.
If the issue continues after trying these steps, please let me know whether you are using a personal Microsoft account or a work/school account.