Troubleshoot email delivery problems

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An error message will usually tell you exactly why an email that you sent could not be delivered. This is called a “non-delivery report” (NDR). It can take up to 4 days for an error message to be created, to allow several attempts at delivery if temporary problems are detected.

For information on specific error messages please see our page on how to Fix “undeliverable” errors when sending email.

There is no guaranteed delivery time for email, even though messages usually arrive within a few minutes. Temporary issues such as servers being busy, maintenance, recipient mailbox being full, and spam/malware detection can lead to multiple delivery attempts.

If a message you sent hasn’t arrived after 4 days, and you have not received an NDR (see above) then your message may have been silently stopped for some reason.

For common reasons why messages you sent might not arrive with the intended recipient, and how to fix them, see ComputerHope's guide "why is my email not getting to the recipient".

See our guidance on managing spam settings. Key options here are adjusting your spam filtering level in Outlook and/or adding the sender to your Safe Senders list.

Messages can end up in unexpected places, so do some basic checks first:

  1. Check your Junk Mail folder
  2. Search for the sender's name. You'll need to do this from the INBOX folder with the search scope set to Current Mailbox and separately from the Deleted Items folder
  3. Ask the sender to reply to a message you’ve sent them - this double-checks that they have your correct email address

If none of these have helped then you should contact your local ITSS and ask them to submit a missing email request.