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e-mail delivery problems
- From: Joe Arnstein
- Date: Wed Feb 21 11:56:33 2001
When one of my sites sends messages with certain attachments, communication
between the client and the mailserver freezes up, and I am having trouble
pinpointing the source. The problem brings up some other questions I have
about extended SMTP transmissions that aren't spelled out in RFC 1869.
When users at a remote site ("BadSite") try to send mail with certain
attachments through our server (or any other server for that matter), the
connection gets dropped mid transmission. I notice in the verbose sendmail
logs that an ehlo is given, headers are sent, then the mime encoded MSWord
doc starts to go through, but in the middle of the transmission the client
appears to just sit until the connection times out. We get a "read error"
in Sendmail, and a time-out error in Outlook. The same thing happens when
using 'mutt' in Linux.
Things I've noticed:
* Problem is isolated to BadSite...They cannot send these attachments
through my server, or anyone else's for that matter.
* Some attachments go through just fine... .jpg, .pdf, .bmp and .txt work
OK. If you change the extension of a good file to .doc, it goes through
fine (it's not like the extension alone is causing the problem). :)
* An EHLO is given when sending files like .doc and others that FAIL, while
HELO is offered every time the good files go through. ESMTP connections
any other lan work fine on my server.
Mail clients at BadSite range from MSOutlook on NT, to mutt on Linux boxes.
We have a Cisco router with no access-lists on it and no firewall.
Is this a problem with the type of transmission (ESMTP vs SMTP)?
Encapsulation? It doesn't seem like a server problem, but I was told it
couldn't possibly be a router problem....not sure where to go from here.
Another question: What determines whether a client sends EHLO or HELO?
Thanks for your input!
<clips from logs follow>
28803 >>> 220 mail.mymailserver.com ESMTP
28803 <<< EHLO client.mylan.com
28803 >>> 250-mail.mymailserver.com Hello client.mylan.com [63.75.xx.xxx],
pleased to meet you
28803 >>> 250-8BITMIME
28803 >>> 250-SIZE
28803 >>> 250-DSN
28803 >>> 250-ONEX
28803 >>> 250-XUSR
28803 >>> 250 HELP
28803 <<< MAIL From:<email@example.com> SIZE=15045
28804 >>> 250 <firstname.lastname@example.org>... Sender ok
28804 <<< RCPT To:<email@example.com>
28804 >>> 250 <firstname.lastname@example.org>... Recipient ok
28804 <<< DATA
28804 >>> 354 Enter mail, end with "." on a line by itself
28804 <<< Received: (from root@localhost)
28804 <<< by client.mylan.com (8.9.3/8.9.3) id PAA12375
28804 <<< for email@example.com; Tue, 20 Feb 2001 15:52:35 -0500
28804 <<< Date: Tue, 20 Feb 2001 15:52:35 -0500
28804 <<< From: localuser <firstname.lastname@example.org>
28804 <<< To: email@example.com
28804 <<< Subject: here we go again
28804 <<< Message-ID: <20010220155235.A12365@client.mylan.com>
28804 <<< Mime-Version: 1.0
28804 <<< Content-Type: multipart/mixed; boundary="n8g4imXOkfNTN/H1"
28804 <<< X-Mailer: Mutt 0.95.4us
28804 <<< --n8g4imXOkfNTN/H1
28804 <<< Content-Type: text/plain; charset=us-ascii
28804 <<< content of message....
28804 <<< --n8g4imXOkfNTN/H1
28804 <<< Content-Type: application/msword
28804 <<< Content-Disposition: attachment; filename="Document.doc"
28804 <<< Content-Transfer-Encoding: base64
<at this point transmission hangs and connection eventually drops>