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Possible Open Relay

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Possible Open Relay - 5.Aug.2005 6:19:00 PM   


Posts: 2
Joined: 5.Aug.2005
From: Fort Wayne
Status: offline
Exchange 2000 sp3 on a win2k sp4 server.

We currently have a third party test out systems for possible vulnerabilitie.

They list us as having a possible open relay.

Below is listed SMTP session names have been changed to protect the innocent:

HELO qualysguard.com
250 [FQDN of my Public Server] Hello []
MAIL FROM:<qgmrfrom@[FQDN of my Public Server]>
250 2.1.0 qgmrfrom@[FQDN of my Public Server]....Sender OK
RCPT TO:<qgmrtest%qualysguard.com>
250 2.1.5 qgmrtest%qualysguard.com@[Internal Domain Name]
354 Start mail input; end with <CRLF>.<CRLF>
QG mail relay test # 22
250 2.6.0 <EXCHANGE01R0rmTIVvL0000049e@[FQDN of my Public Server]> Queued mail for delivery

It then will produce a NDR because qgmrtest%qualysguard.com@[my internal domain name] doesn't exist.

It appears when you use a % instead of a @ in the RCPT command it forces it to use the internal domain name of the exchange server.

Is there a way to plug that hole?

Thanks in advance.
Post #: 1
RE: Possible Open Relay - 5.Sep.2005 2:07:00 AM   
Henrik Walther


Posts: 6928
Joined: 21.Nov.2002
From: Copenhagen, Denmark
Status: offline
Some of these web-based tests list you as a possible open relay although you're not.

But to make sure your Exchange 2000 server is configured properly see below article.

Understanding Relaying and Spam with Exchange 2000:

(in reply to honster)
Post #: 2

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