Mail from: shows internal server name in mail header and fails -- iis smtp nntp

skyline
9/13/2005 5:59:02 AM

The SMTP server generated the NDR. Both servers are allowed to relay through
the SMTP server and many clients get the emails from the new application
server but some do not.

We are investigating the following link as this may relate to the problem:

http://www.dylanbeattie.net/docs/iis6_bare_linefeed.html

Although we did not upgrade the version of IIS the new application server is
running a .NET app different from the Adobe application on the first app
server to generate the emails and I have the sneaking suspesion they
programmed it incorrectly.

Thanks for the reply and if you have any other thoughts please let me know.

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Al Mulnick
9/13/2005 9:15:53 AM

Just for fun, is the destination mail server the same? Because the DSN
indicates that it couldn't contact the destination and therefore gave the
message back. Is there a syntax error, or other?

What are they using to generate the email in .NET? Are they hand-crafting
the conversation (reinventing the wheel) or using some of the built in
functions?

Al

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Al Mulnick
9/14/2005 12:00:00 AM

It's absolutely possible to filter by IP address. It's on the properties of
the SMTP server under the access | relay tab (something like that :)

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skyline
9/14/2005 8:45:18 AM

The current workaround/resolution is to move this custom made application
over to the original application server and it works like a charm. No
changes to the application were made

Both systems are Windows 2000 with matching network properties and as far as
I can tell they are configured the same.

The custom application is using .NET's email function. From what I can tell
it is a rather simple app designed just to send emails. The destination mail
servers are of all types, however the domains reporting problems are not
Yahoo! users (they receive fine) but more specific smaller hosting companies
such as lightbound.com are getting denied. Here is one of the errors from
the system log:

Message delivery to the host '206.246.140.84' failed while delivering to the
remote domain 'lightbound.com' for the following reason: The connection was
dropped by the remote host.

Is it possible to filter by an internal IP in an email header (or a server
name)? In the end of the initial hand off in the header you can plainly see
our mail servers DNS name as the sender. The only difference is the HELO
command to our internal server which I can't imagine is a problem. The IP is
granted relay access just as the other one, and no errors are returned when
sending.

I find it super odd that the messages make it to the SMTP server and out to
the destination but are dropped at that point. It gets to the DATA command
and then never issues a quit so I am assuming that it dies during this time.

All of the failure notifications simply give the 4.4.7 action failed status
on return which is the code for a delay. The email addresses in the failure
notification have the text RFC822 in front of each address. I thought we
must be violating a procedure in that RFC but there are so many listed I have
no way of telling which one(s) we may be violating.

The people that receive the messages do not report them being different or
bad and of course there is the handfull that simply don't receive them.

We have worked around by putting back on the original server but it is still
a necessity to figure out where the problem is here.

Thanks for your help!

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skyline
9/14/2005 8:58:02 AM

By the way the error from the system log is the log of the SMTP server.

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skyline
9/14/2005 10:45:06 AM

Possible on the receiving end to filter by our internal application IP
address? As far as our SMTP server we are allowing the internal
communication but I did not know it was possible to deny on the receiving end
based on our internal IP of the app server. Can you confirm that?

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Al Mulnick
9/14/2005 2:24:11 PM

I should have read more closely. :)
You *could* filter by the ipaddr of the MUA, but you'd have to do that at
the first hop (in otherwords, the first server to receive the mail) else
have a program that looks for that specific information. I wouldn't expect
it to be useful though as that information would not be considered stable in
my opinion.

If the message is received by your local server (same as the other
application) but is then denied at the next hop, then you need to look at
the recipient host or the communication between it if there is a SMTP-aware
firewall between for the issue.

client-application --->MTA1 (your server) --->MTA2 (Host: '206.246.140.84';
refuses to take the mail 4.2.1).
Is that the correct way to express the problem? If so, then '206.246.140.84'
is the host to check first and work your way back. Check the logs to see
why it was rejected and what it objects to.

Al

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skyline
9/15/2005 6:24:03 AM

I've noticed a new link in the chain. Inspecting most of the failed domains
I have found a common link: those denying our mail seem to be running
SquirrelMail and not Exchange/GroupWise/etc.

client-application --->MTA1 (your server) --->MTA2 (Host: '206.246.140.84';
refuses to take the mail 4.2.1).

That would be the correct route. I have been through our logs with a fine
tooth comb and see no real "reason" why we are getting denied. Since most of
our clients are with a hosting company I am having to seek help from them to
find out why they would deny us and as I am sure you know this is not easy
since we are not customers. One is cooperating but rather slowly....so maybe
I will get an answer through them.

I appreciate your help and will post any additional findings or resolution
if I can get one :)

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Al Mulnick
9/15/2005 9:44:00 AM

You might want to trace the network between MTA1 and your egress point in
the meantime. Look for things like EHLO conversations and missing CRLF
combinations and look for the conversation ending verbs and data etc.

Might prove useful to see the conversation as it occurs regardless of what
the hosting company says. :)

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iis smtp nntp : Mail from: shows internal server name in mail header and fails