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High volume of outgoing emails being relayed through Exchange

Posted on 2008-10-07
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Last Modified: 2013-11-30
Hi there, we have a HUGE amount of email (which I've only just noticed) being sent out through our client's exchange server.

I logged into OWA, and noticed there was arround 40000 emails in the inbox, nearly all of them were bouncebacks from various people. I then checked Exchange tracking centre, and its just spewing out loads of emails.

I'm pretty sure open relay isn't enabled on the server, as I've compared the config with another SBS server.

is there anyway I can track where these emails are being sent from? Perhaps they are coming from a client with a virus on.

I'm surprised they haven't been blacklisted...

ANy help would be much appreciated.
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Question by:dougb9429
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Expert Comment

by:sgsm81
ID: 22659980
Check any firewall rules on port 25 to see if it is locked to a particular IP range.

Check the e-mail headers - http://www.stopspam.org/email/headers.html

Do you have e-mail antivirus client for outlook or similar - might be worth a scan..
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Author Comment

by:dougb9429
ID: 22660013
Hi there, thanks for your reply.

Is there any way I can check the headers of the emails that have been sent out? Either thru OWA or through Exchange??

I will kick off a scan straight away.
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by:sgsm81
ID: 22660054
Hi

Have you enabled e-mail journalling at all ? if so this would keep a copy of everything that was sent ?

Do you use a hosted anti spam solution or similar e.g. e-mailsystems ?
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Author Comment

by:dougb9429
ID: 22660076
No journaling isn't enabled...

And no, we use GFI Mail Essentials for anti spam.

I suppose if I enable journaling now, it will still pick up email, then I guess I could read the headers of that?
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Author Comment

by:dougb9429
ID: 22660285
I've enabled journaling, and it's picking up other emails, but all the emails being sent from the administrator account are not being journaled, despite them all showing in the exchange tracking centre.
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Expert Comment

by:sgsm81
ID: 22660490
What version of exchange are you running and how have you enabled journalling ?

(sorry but dependent on the version there are a few ways to do it).

Also can you see if the mails are being sent from one account ? if so is it possible to disable that account's mailbox whilst the problem is diagnosed.
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Author Comment

by:dougb9429
ID: 22660542
It's 2003 on an SBS Server (SP2)

I set up a new user for journaling, right clicked on the mailbox store, and selected archive sent/received messages.

The account is actually the administrator account. It has a secondary email called postmaster@ and all the emails are being sent from there.
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Expert Comment

by:sgsm81
ID: 22666901
Did you find anything from the e-mail headers which indicates the sender/recipient of mail sent/received ?

Have you checked your 2003 server to ensure its not a relay?

I'd also consider enabling advanced journaling to cover BCC, Distribution lists etc

http://www.microsoft.com/downloads/details.aspx?familyid=e7f73f10-7933-40f3-b07e-ebf38df3400d&displaylang=en
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DSchel01 earned 500 total points
ID: 22668387
Most likely the they are NDR messages caused by NDR (or back scatter) spam.

Ensure you are on at least the latest build of GFi MailEssentials 12 (20080623) which includes the NDR spam functionality. Make sure to leave the New Senders functionality disabled, but set the action to delete. This will prevent NDR spam from being received by end users in future.

Also, if you have maintenance consider upgrading to MailEssentials 14. This version of MailEssentials includes a new antispam engine, spamrazer, which considerably improves the performance of MailEssentials spam detection. MailEssentials 14 can also filter directory harvesting emails at the protocol level, which will greatly reduce the amount of email accepted by your mail server.

More information:
How to check for NDR spam (BackScatter)
http://kbase.gfi.com/showarticle.asp?id=KBID003322

What's new in GFI MailEssentials 14 for Exchange/SMTP?
http://kbase.gfi.com/showarticle.asp?id=KBID003400
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Author Closing Comment

by:dougb9429
ID: 31503817
After uninstalling and reinstalling GFI it seemed to work! Thanks for putting me on the right track!
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