Trying to send one email to multiple addresses which gets rejected

Outlook.com’s sending quota cannot be manually removed, but updating the account’s security/profile information and building normal sending history can raise a temporarily reduced limit.

A message sent to 25 addresses counts as 25 recipients toward the quota; splitting the message only works around the current restriction rather than removing it. Outlook.com applies both a daily-recipient limit and a per-message recipient limit. For Microsoft 365 subscribers, the documented maximums are 5,000 daily recipients, 500 recipients per message, and 1,000 daily recipients with whom there is no prior email relationship. Actual limits can be lower for non-subscribers and can vary with usage history.^1^

Steps to restore a higher limit

1. If sending is currently blocked, wait for the temporary restriction to expire.
   Similar Outlook.com quota blocks generally reset after approximately 24 hours.^2^
2. Update the Microsoft account’s security information.
   Ensure the phone number and alternate email address are current.
3. Complete the Outlook.com profile information.
   Check that the profile name and other requested details are populated.
4. Add the 25 recipients to Outlook.com Contacts.
   Outlook.com distinguishes “non-relationship recipients”—people the account has never emailed—from established contacts. Communicating normally with saved contacts helps establish account credibility.
5. Enable Microsoft Authenticator for the account.
   Microsoft lists Authenticator as another way to verify identity and help increase sending limits.^1^
6. Resume sending at a steady rate after the restriction clears.
   If the account is new, its low quota is temporary and should increase as credibility is established. Until then, continue using smaller groups, but do not repeatedly retry a rejected 25-recipient message.

If the address used in Outlook.com is actually a connected Gmail, Yahoo, or other third-party account, that provider’s sending limits apply instead.^1^

If 25 recipients continue to be rejected

In Outlook.com, select Help on the menu bar, describe the sending-limit error, and—if self-help does not resolve it—scroll to Still need help? and select Yes to contact Outlook.com support.^1^

Include the rejection text, when it occurred, whether the account is new, and whether it has a Microsoft 365 subscription. Do not include the recipients’ addresses in a public forum.

References

1. Sending limits in Outlook.com | Microsoft Support
2. Outlook.com has blocked your message - Microsoft Q&A