Embedded graphics in mails

[stonedog]

Hey all, this sounds like a question from an MCSE exam but I promise you it isn't.

We have an Exchange 5.5 SP4 server serving users on several different sites through either LES10 circuits or straightforward fibre runs. We run the Internet Mail Connector to our outbound mail router. All our servers run the Trend Anti-virus suite.

One site in particular (I'll call it Site A and the server home Site B) uses embedded graphics in their emails as e-flyers to advertise events and festivities. Here's where the fun starts.

1) Users at Site A can send the embedded graphic without any problems to users at Site B - and vice versa.

2) Users at Site A have problems sending the same mail with the embedded graphics to external addresses. Users at Site B don't have problems sending the same mail with embedded graphics.

3) If we log onto a PC in Site B with a user account from Site A the mail goes OK from that users account.

4) If we log onto a PC in Site A with an account from Site B it doesn't work even though it does work at Site B.

All mail goes through the same core network router, the same mail server, the same IMC, and the same mail router. We've tried changing the version of Outlook we're using and the results stay the same. PC settings are identical at both sites. The server is setup to allow HTML format mails in both the IMC connections config and the POP protocol config.

I'm absolutely stumped, so any help would be greatly appreciated.

 

[NetIntruder]

Well that's a good one

Do you have any computer policy applied to Site A? based on the problem you have here, let's start there first...

~Intruder~
CEH, MCSA/MCSE 2000/2003

"The Less You Do, The Less Can Go Wrong"

 

[stonedog]

Nope - no policies of any description at all.

 

[NetIntruder]

ok, terrific. Any anti-spam filtering software?

~Intruder~
CEH, MCSA/MCSE 2000/2003

"The Less You Do, The Less Can Go Wrong"

 

[stonedog]

We use InterScan Messenging Security Suite on our mail routers. On the Exchange side we use Trend and it's associated Exchange Agent.

 

[NetIntruder]

well, i'm not familiar with InterScan, but it sure sounds like there's a setting to block HTML at the IMC for a site... just a shot here, but are there any settings in InterScan that can filter what format can be sent (specifically based on site..)?

~Intruder~
CEH, MCSA/MCSE 2000/2003

"The Less You Do, The Less Can Go Wrong"

 

[stonedog]

I'm afraid not. We have three Exchange 5.5 servers but all outbound mail is routed through a single bridgehead box, and this is the only server that routes mail to the outbound mail router.

 

[NetIntruder]

hmm... i'll toss this around my department and see if anyone digs anything up here...

~Intruder~
CEH, MCSA/MCSE 2000/2003

"The Less You Do, The Less Can Go Wrong"

 

[stonedog]

Thanks mate, it's been doing my brain case in for the last month. I've spoken to our network monkeys to see if they've got any packet filtering going on but they run a LES10 circuit straight into the same core router we use on this site.

Any help would be greatly appreciated.