Outlook.com is blocking messages because the sending limits for that account have been reached. Outlook.com limits how many recipients can be included in messages to reduce spam. When the limit is exceeded, sending is restricted until the number of recipients is reduced or the account gains more sending credibility.
To restore sending and receiving:
- Reduce recipients on current messages
- Edit the message and remove some recipients from the To/Cc/Bcc fields.
- Send to smaller groups instead of one large list.
- Verify the Outlook.com account
- Follow the guidance in the message to verify the account identity. Verifying the account helps increase the sending quota and reduces interruptions. For more information about sending limits, see Sending limits in Outlook.com.
- Check for other send issues
- If messages still do not send after reducing recipients and verifying the account, review other common causes:
- Ensure attachments are not larger than 25 MB; larger attachments will prevent sending. See Unable to attach files in Outlook.com if needed.
- If a non‑delivery report (NDR) is received, check the reason in the NDR (invalid address, recipient mailbox full, server issues, or spam filters) and correct accordingly.
- Ask recipients to add the address to their Safe senders list if messages are being filtered as spam. See Safe Senders in Outlook.com.
- If the account is new
- New Outlook.com accounts have a lower temporary sending quota. As normal usage continues and the account builds credibility, the quota is automatically increased. Details are in Sending limits in Outlook.com.
These steps address the sending restriction so business mail can resume once the account is verified and messages stay within Outlook.com’s sending limits.
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