Undeliverable email lost

Dear Jeremy,

Unfortunately, as a forum moderator, I am not able to inspect your mailbox or trace the message to locate it for you directly. My role here is limited to general guidance you can apply from your side. Before suggesting anything, it would help to know what you are trying to recover, as "retrieve" could mean either getting back the original message you sent, or getting it delivered to the recipient. Those need different approaches. Could you share a few details:

• Are you after the original message content, or do you want it to reach the recipient?
• What is the exact wording of the bounce message, including the NDR code such as 5.1.1 or 5.7.1? That single detail usually explains the cause outright.
• Have you checked Sent Items, Drafts, and Deleted Items?
• Is this a personal Outlook.com account or a work or school account?

In most cases the original text is still recoverable, since the non delivery report normally includes the message as an attachment, and a copy usually remains in Sent Items even when delivery failed.

Share those details and I can point you to the right next step.