sendmail returns message when TCP fails

[nowicki%coyote at sri-unix.UUCP]

From:  Bill Nowicki <nowicki at coyote>

Description:
	Recently we have been having congestion problems in our
Arpanet gateway.  This causes packets to be dropped, and eventually
TCP connections to time out.  The sendmail SMTP daemon will return
a message to the sender when the TCP connection times out during
transmission.  It should instead just discard the partially-received
message, since the sending host will send it again the next time
the queue is run.  This bug causes our users to get copies of their
outgoing mail returned hourly until the evening when our gateway
congestion disappears and the message finally gets delivered properly.

Repeat-By:
	Send a large message from host A to host B, (say, "nobody at B")
where host B is running sendmail.  After doing netstats on either host
to determine that a TCP connection has been made, do a ps on host A
and kill the sendmail process quickly before it completes.  You will
get a message back from mailer-daemon at B saying "SYSERR:unexpected close".
The next time the queue is run, however, the message is successfully
delivered to the user on host B.


Fix:
	change the line:
		syserr("collect:unexpected close");

	to the block:
	  {
		syserr("unexpected close, from=%s", CurEnv->e_from.q_paddr);
		CurEnv->e_flags &= ~EF_FATALERRS;
		finis();
	  }