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Exchange Attachment Restrictions

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25 replies

by mkowitz

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This issue just popped up, and I am wondering if anyone has a suggestion:
I administer Exchange 2003 for <100 users. About a year ago I started enforcing global message size limits to 5Mb incoming and outgoing, with a few "power" users excepted to 7.5 or 10Mb limits, which worked just fine. Just recently (within the last week) something changed in that these users with expanded limits are not able to email attachments larger than the (global) 5Mb limit to outside customers, but are able to send internally to each other. The settings--global and individual--have not changed. Anyone have a clue where I should look, or a method of troubleshooting this?
Thanks,
mk

25 replies

by maniacman

That would be the first thing I'd look for, because it does sound like some strange bug is doing this. I do agree with you that settings at the user level should override the global settings for those specific users who are allowed to send attachments over 5MB in size. Hmmm...have you tried contacting MS to see if they're aware of this and may have a hotfix for it?

by bart777

I would try to contact the administrator at the other end of the conversaion and see if they have a limit on incoming files. If the limits work internally but not externally then you have a problem at the other end or some strange setting in a router on your side. (Not likely I would imagine)

by mkowitz

. . . if I do a trace, using Exchange Manager, I see the message get submitted to all of the queues, etc, but it never get delivered to the other system before the NDR is generated, and the recipient has been contacted, and they are not having problems receiving other attachments (>5Mb). (?!?!?)

by dumphrey

restrictions and exceptions? I would reset them to the values you want just to be sure.
And you are right, the NDR where it is mewans its on your end. Have you double checked access rights and black lists? And do you know if the trouble is isolated to only a few senders/receivers or is it global?

by locolobo

I figure you have but it was a thought. ManiacMan brings up a more likely point about patches and upgrades.

by dumphrey

but I would also check spam filter appliances etc that may be scanning any outgoing mail. The most likely place for problems are spam filters and the mail server its self. Since it works internally, its probably not the mail server, but just to be sure, I would check the mail settings again on the smtp ptotocol, as that part would not be called into play for local service/delivery.

by mkowitz

I've checked the properties of the SMTP connector and the SMTP protocol virtual machine, and everything looks right. Is there any other places I should be looking? (I was on that track also, since it appears different between internal/external).
Does anyone know which services (if any) I can restart, in lieu of a complete reboot?

by kjell_andorsen

Do you use any kind of spam filtering firewall or SMTP gateway appliance? Often these appliances have their own settings regulating attachment sizes etc. Also some software anti virus/spam mail security suites have settings that regulate message sizes and contents. You might also want to check there.

by dumphrey

Prefaced with Microsoft Exchange. Restart those and then restart Simple Mail Transport Protocol. Imap and POP3 are exchange protocols but SMTP is a stand alone service.
A good reboot would be better but restarting services is quicker. I do not guess any firewalls on the server?

by mkowitz

Globals are in Exchange Manager: (Exchange)-->Global Settings-->Message Delivery-->Details tab.
The exceptions are in AD Users and Computers: Users-->-->Exchange General tab-->Delivery Restrictions.
I'm aware of the problem with two of the users that are excepted from the globals.
I don't believe blacklists are an issue since smaller messages get through OK.
I'm going to try a reboot tonight just to eliminate that possibility.

by dumphrey

size limits on the smtp ptotocol in
System Manager --> Admin Groups --> First Admin Group --> Servers --> (server name) --> protocols -->SMTP --> Default SMTP virtual server properties. It should over ride globals if its set.

by mkowitz

All of the items in the Messages tab are unchecked--which I assume will then use the defaults.

by kjell_andorsen

Have you checked the user accounts in ADUC to make sure someone didn't reset their accounts to use the default when it comes to message size?

by mkowitz

I'm the only one who gets in there, and yes I did verify.

by mkowitz

I will try this and let everyone know.
Nope, have an unattached firewall.

by dumphrey

with spam/av appliances? any thing like that on your outgoing mail?

by mkowitz

I have Symantec AntiSpam for Exchange, but nothing has changed on that, and why would it check outgoing mail? But not internal mail?

by cbabbage

From what you provided:
- Internal mail any size works fine.
- Outbound Mail delivery generates NDR for mail >5Mb.
- SMTP settings for Exchange appear (assumed) OK (non-restrictive)

With the above, I would suggest that you take a closer look at email that crosses your gateway boundaries and review the dependencies between the SMTP and the mail gateway filter. The problem is localized to the gateway SPAM/AV Filter because that is facing the internet. A starting point will be to:
- return the internet facing mail filter to factory default settings or "pass-through" mode
- reconfigure local info name, dns, etc
- rebooot
- conduct a test to a gmail or other non restrictive external public domain account

The exchange account settings appear OK in so much as the users can communicate unrestricted internally.

You will also need to be sure that there is no other intermediate layer security appliance such as an IDS/IPS that is filtering traffic at a lower layer to interfere with email content and traffic.

This appears to be a "Symantec thing" as I know of other installations undergoing similar experience.

Good luck

by mkowitz

. . . and no luck. Shut down anything with Exchange in it's name and the SMTP service, then restarted all, and the same thing is happening. I will reboot the server tonight. I'll post results then.
I thank you all for your input!

by mkowitz

A reboot didn't help (I also applied the latest monthly updates and patches-I suppose adding more variables to the mix-but, If no one else is having issues with MS updates, why should it affect my system?). I'm actually in other offices the rest of today, but I'm open to suggestions. Thanks again all.

by locolobo

but I don't think its a good one. What if you specifically set the size limit in the SMTP properties to the upper limit? My question then is will the default limits in Exchange limit most users yet now allow the super users to email their attachments?

Probably not a good idea, but you might try it strictly as a test to see what happens.

by dumphrey

would elimate Exchange being the culprit, and let you/us focus on other ideas such as spam/av gatways and programs.

If you remove all size limits, and it still happens, its not exchange but another component in the chain. This should take maybe 15 min to check.

by mkowitz

And I will give it a try first chance I get, and let you know.
Thanks again!

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