sendmail can lose forwarded mail

[Jeff Stearns]

Index:	usr.lib/sendmail 4.2BSD

Description:
	Under certain conditions, sendmail will discard mail which is to be
	forwarded to another machine.

Repeat-By:
	Let there be two machines A and B, connected by ethernet.
	Let there be a user U with accounts on both machines.
	On machine A, let this user have a ~/.forward file which redirects
	mail to "U at B"
	Now have U log in on machine B and send mail to "U at A".
	The mail will be discarded upon receipt at machine A.

-------------------------------------------------------------------------------
	I have some additional clues.  Here's an (electronically enhanced)
	syslog transcript produced by the daemon sendmail which received the
	letter at machine A.  (I added the syslog() calls beginning with `--'
	in order to produce additional debugging information.)

	Note that the letter is never passed to any outgoing mailer for
	forwarding or delivery.

		/*
		 * Sendmail hears an incoming ethernet letter.
		 * It forks to read and process the letter.
		 */
	7588 sendmail: connected, pid=7588
	7588 sendmail: : openx
	7588 sendmail: AA07588: assigned id
	7589 sendmail: : openx
		/*
		 * The incoming letter is received via SMTP at machine A, and is
		 * assigned a queue id.
		 */
	7589 sendmail: AA07589: assigned id
	7589 sendmail: AA07589: from=<jeff at tc-jeff>, size=172, class=0
	7589 sendmail: --sendall: e=83080 mode=b
		/*
		 * The received message is deposited in the mail queue.
		 */
	7589 sendmail: AA07589: queueup, qf=qfAA07589, df=dfAA07589
		/*
		 * A child is forked to deliver the message in the background.
	 	 */
	7593 sendmail: in background, pid=7593
	7593 sendmail: --sendall: Run through list and send everything...
	7593 sendmail: ----sendall: mode=b
	7593 sendmail: ----sendall: calling deliver(83080, 163716)
		/*
		 * The child discovers that QDONTSEND is asserted for the
		 * recipient, so it makes no attempt to deliver the letter.
		 * (I don't know *why* QDONTSEND is set on this envelope.)
		 */
	7593 sendmail: --deliver, first user=`jeff' (QDONTSEND)
	7593 sendmail: ----sendall: mode=b
	7593 sendmail: ----sendall: calling deliver(83080, 163844)
	7593 sendmail: --deliver, first user=`jeff at tc-jeff' (QDONTSEND)
		/*
		 * The child now REMOVES THE LETTER FROM THE MAIL QUEUE!
		 */
	7593 sendmail: dropenvelope, id=AA07589, flags=0, pid=7593
	7593 sendmail: AA07589: unlink dfAA07589
	7593 sendmail: AA07589: unlink qfAA07589
	7589 sendmail: finis, pid=7589
		/*
		 * The parent removes the lock file, and everything's gone.
		 */
	7588 sendmail: AA07588: unlock
	7588 sendmail: AA07588: unlink lfAA07588

Fix:
	I know of none.  Clearing the `e' (expensive mailer) flag for the ether
	and local mailers does not help.
-- 
	Jeff Stearns
	John Fluke Mfg. Co.  (206) 356-5064
	P.O. Box C9090  Everett WA  98043
	...!decvax!microsoft!fluke!jeff