Determining the Cause Of An E-mail Bounce

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Determining the Cause Of An E-mail Bounce

The "transcript" that is contained in the rest of the above message provides the main clues -- sometimes obvious, sometimes obscure -- to what actually happened. Additional evidence can also often be found in the bounce's Subject: line, which often contains a useful excerpt from the transcript (shown in bold in the table below).

Here are some of the many cases that have passed through our Office of Information Technology (OIT) Help Desk. Not all lines shown below may appear in a given incident, and sometimes a mail server will add others, such as our WAM server's

... while talking to poN.wam.umd.edu .:

Session-transcript	Other specifics	Explanation
>>> RCPT To:<recipient's-address> <<< 550 <recipient's-address>... User unknown 550 <recipient's-address>... User unknown	--	Recipient on the To: line is misspelled, or no longer has an account at that address
550 <recipient's-address>... *Host unknown (Name server: recipient's-host: host not found)*	--	Recipient's host-name on the To: line is misspelled, or its name-server is down
>>> MAIL From:<sender's address> <<< 550 Access denied . . . followed by one of three reasons here at the right `--->` (You can confirm this problem without having direct access to the bounced mail if you have the sender's address.)	`550 Sorry, no access for this ip`	Sender is from a known spam IP-address
	`550 Sorry, no access for this domain`	Sender is in a known spam domain
	`550 Sorry, no access for this user`	Sender is a known spammer
550 /directory-path/.forward: line 1: (contents of line 1) ... Can't create output: Permission denied	--	The recipient has a .forward file containing an unreadable address
>>> DATA <<< 553 user address required < 554 <recipient's-address>... Service unavailable or 451 From:domain must resolve	--	To: or From: line has an improperly constructed address.
553 <recipient's-address> ... unauthorized relay traffic prohibited 554 <recipient's-address> ... Service unavailable	--	Sender is relaying mail -- probably using a commercial ISP while using a UM From:-address
554 sendall: too many hops 19 (17 max) (the numbers may vary, and addresses may be included)	--	There is a mail loop -- probably the recipient has mail forwarded to another account, which has mail forwarded back to the original account
<<< 553 Header Error 554 recipient's-address... Service unavailable	--	This can be pretty obscure. There is a non-parseable line in the header, but finding it can be difficult. One example: `Resent-Message-ID: <"s3rGDD.A.saG.tTjM1"@earth.mat.net>` where a more standard message-id might look like this: `Message-Id: <3.0.5.32.19980413115110.0082e9a0@tir.com>`
>>> DATA <<< 553 Header Error 2 554 recipient's-address... Service unavailable	--	This "Error 2" may be a non-standard patch by the local postmaster to stop certain mail (e.g., used here to stop all messages with "Hi" in the subject line during a mass-mail battle)