An email I was sending to people I know got blocked

Try these checks in Outlook.com, in this order:

1. Check whether the message has a large attachment.
   • Outlook.com cannot send a message if an attachment is larger than 25 MB.
   • Remove the attachment and send again.
2. Review any delivery failure or blocked message details.
   • If Outlook returned a failed delivery or postmaster message, open it and scroll to the diagnostic section for the reason.
   • Common causes include an invalid recipient address, a full recipient mailbox, server issues, spam filtering, or an attachment that is too large.
3. Verify each recipient address.
   • Delete the recipient from the To field.
   • Start typing the address until it appears in Auto-Complete.
   • Delete the Auto-Complete entry.
   • Re-enter the full email address manually and resend.
   • This helps if Outlook saved an outdated or bad address.
4. Reduce the number of recipients and resend.
   • Delivery failures can happen when too many recipients are included in one message.
   • Send to a smaller group first.
5. Remove the email signature and try again.
   • A signature can sometimes affect sending.
6. Make sure the recipients are in Contacts.
   • Add the people being emailed to Contacts in Outlook.com.
7. Ask recipients to add the address to their Safe senders list.
   • This can help if the message is being filtered.
8. If the account is new, check for temporary sending restrictions.
   • New Outlook.com accounts can have a lower temporary sending quota until account credibility is established.
9. If the issue is specifically sending to an Outlook.com or Hotmail recipient, improve sender reputation.
   • If antivirus email protection is enabled, disable Internet Email Auto Protect or Internet Email Protection and test again.
   • Send an email to the same account, open it, and reply to it.
   • Avoid sending too many emails at once or putting all recipients in BCC.
10. If a non-delivery receipt was received and the recipient address is correct, use Sender Support in Outlook.com.

If the error says the message was blocked or listed by a blacklist on the recipient server, the recipient’s email provider support team must unblock the account or domain.

• Can't send or receive email in Outlook.com
• Sent email in Outlook.com comes back "delivery failed"
• Failed delivery messages from the postmaster at outlook.com, microsoft.com, or service.microsoft.com
• Sender Support in Outlook.com