An email bounces (NDR): delivery failed
The NDR text usually states the exact reason. Reading it is step one.
Try this first
- 1Open the NDR message and look for a line like "550 5.1.1" or "Recipient address rejected". That is the reason in two words.
- 2Typo in the address: open the mail in Sent Items and resend with the right address. Tip: add to contacts so Outlook auto-suggest stops misfiring.
- 3"Mailbox quota exceeded": the recipient has a full mailbox. Phone or text them so they know.
- 4"5.7.1 message rejected as spam": your sender is being refused. See the spam-delivery section.
- 5"DNS lookup failed": the receiving domain does not exist or is broken. Nothing you can fix from here.
When to bring us in
If your own domain is named in the NDR as the rejecting party (your own filter pushing back); we can look inside your tenant.
See also
- Our emails land in spam for some recipientsAlmost always an SPF, DKIM, or DMARC setting that is wrong or missing, or a sender name that mimics a well-known brand.
- Someone reports receiving phishing emails "from us"Read: spoofing. Someone is abusing your sender name, not necessarily your actual mailbox.
- The domain scan says SPF/DKIM/DMARC is missing: what does that mean?Three small DNS records that tell receivers "this server may send on my behalf". Without them you are an open invitation.
None of the above fits?
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