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Exchange 2007 Sender Policy Framework

Posted on 2009-05-06
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Hi. We are looking at increasing our security and one of the tasks is to deny hackers that TELNET to our mail server via port 25 and send an email from a user thats on my domain to another user thats on my domain. If an hacker does this the originating IP will be external thus this must not be allowed. However, I tried changing some settings in Exchange 2007 under Receive connectors but then my emails start queing up so i had to reverse my changes. Please advise. I dont want to change port 25 nor do I want to deny telnet, i believe its IPs allowed in receive connectors that i have to change but how.Thanks
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Question by:BSTIT
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5 Comments
 
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Expert Comment

by:Rajith Enchiparambil
ID: 24312387
If you are so concerned, why don't you disable telnet acces on your firewall and open it only when you need to test something?
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Accepted Solution

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gupnit earned 1000 total points
ID: 24312459
Hi,
Exchange 2007 is secure by default and is not an open relay, unless you make changes to it. Can you please show me some mail, that you suspect. You should not be thinking about blocking port 25, as your mail flow will be hampered.
Thanks
Nitin Gupta (gupnit)
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Author Comment

by:BSTIT
ID: 24312587
Hi qupnit. Let me give you an example. User A on my networks email address is userA@domain.com and User B on my network is userB@domain.com. If a hacker telnets to my exchange server on port 25 and then sends an email from userA@domain.com to userB@domain.com requesting him to transfer money urgently to a bank account. userB will not know its a hacker and will then transfer the money which is a huge security risk. We cant blcok userA email address because its valid but surely there is a way to block an email address if its an internal email address but is not from an internal Ip address
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Author Comment

by:BSTIT
ID: 24313103
HI All. Thanks but i found the solution. We basically added the Anti Spam Ip's to our firewall whereby we allowing only mails from these IP's over port 25. Now if i telnet from the outside to my exchange server it denies access. PERFECT....thanks
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LVL 32

Expert Comment

by:gupnit
ID: 24313489
Great
Cheers
Nitin
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