Unable to send emails or receive

For Outlook.com or a Microsoft account in new Outlook for Mac, check these in order:

1. Check whether cloud storage or mailbox storage is full. If Microsoft cloud storage is full, email cannot be sent or received, and messages sent during that time are bounced back to the sender and are unrecoverable.
2. If the password was changed recently, sign in again with the updated password. A recent password change can stop mail sync until the new credentials are entered.
3. Check whether the account has been temporarily blocked because of unusual sign-in activity. If so, unblock the Outlook.com account.
4. If a message is stuck, check Drafts or Outbox.
5. If an email has an attachment larger than 25 MB, remove it, use a smaller file, or upload it to OneDrive and send a link instead.
6. If mail is not being received, check:
   • the Other tab
   • the Junk Email folder and junk settings
   • Filter > Sort > Date to restore chronological order
   • whether email forwarding is enabled
   • whether any email rules are moving or hiding messages
7. If only one device is affected, removing the partnership between the mobile device and the mailbox can fix sync issues.
8. If sign-in is failing, use the Microsoft account sign-in helper.

If using Outlook on PC or Mac with an Outlook.com account, also run Send/Receive > Send/Receive all folders.

Because important employment email may already have been bounced if storage was full, checking storage first is the highest-priority step.

References:

• Can't send or receive email in Outlook.com
• Email stuck in Outlook.com
• I can't send or receive messages in Outlook