Can't send email to certain domain... Host Unreachable

[stevenriz]

Hello, in 5.5 Exchange Server Administrator, Internet Mail Server, Queues, Outbound Messages Waiting for Delivery... I have a few legitimate emails sitting there with the "Host Unreachable" message when looking at the details of the message.

What could this mean? I am able to send email to them using my yahoo account just fine. Any help would be appreaciated! Thanks!
Steve

 

[stevenriz]

I turned on SMTP logging to max and now it shows up in the LOG file as such....

F:\exchsrvr\imcdata\log>grep hillnmarkes *.LOG
L0000000.LOG:7/26/06 10:03:15 AM : 499 Host unreachable: hillnmarkes.com. Message subject: ""RE: test"". Rescheduling delivery for later.


I do believe they are using some email scanning service called PAETEC. I will start my research with them... Thanks!
Steve

 

[dennisbbb]

Do you use a SMTP gateway to relay messages, such as a spam filter server?

"Host Unreachable" is usually a result when the destination host is offline or simply unreachable at the time. But when Yahoo mail can send to the host, and you can telnet manually as well, I believe there is a problem. Your event log may also have a lot of "The connection was dropped by the remote host."

Check this link:

http://support.microsoft.com/default.aspx?scid=kb;en-us;286673&Product=iis50

 

[HupAhh]

Try this post

http://www.tek-tips.com/viewthread.cfm?qid=800289

 

[stevenriz]

Thanks HupAhh, I will take a look at this. In the mean time, I just got off the phone with Message Labs and they told me we are on a high spam list which translates to me to be a black list. Or a brown list haha. Anyway they explained to me what is happening, but not how to fix it if it can be fixed at all.

They claim that when they send a message to our mail server addressed to a recipient that doesn't exist, the server replies with spam along with the message itself. It DOESN'T give an invalid recipient error or an unable to relay error like I guess it should. They think we need to stop accepting mail for invalid recipients.

Question is, how do I do this? We are Exchange 5.5 SP4 relaying is all off. Is this server infected do you think? Are there additional patches past SP4 that I need to get?

 

[dennisbbb]

Perform a relay test on your server here.

http://members.iinet.net.au/~remmie/relay/

I find this suggestion helps clear up this "Host Unreacheable" issue. Put the affected server domains onto manual DNS under IMS/Connections/Specify by E-Mail Domain/

Your store.exe version should be at 5.5.2658.25.

http://www.microsoft.com/downloads/...3B-0489-48DA-B566-6F1343B9F010&displaylang=en

 

[stevenriz]

yes the server is all up to date with that store patch.... the relay tester didn't work. I used some others. This one in particular

http://www.abuse.net/cgi-bin/relaytest

...

All but one test shows relaying prohibited. This last test shows this... And this seems to be what my friend at Message Labs is talking about.... that last 250 OK should be 500 unable to relay.... I really don't know if this is a problem or not. I certainly haven't found a fix yet....

Relay test 6
>>> RSET
<<< 250 OK - Reset
>>> MAIL FROM:<spamtest@test.com>
<<< 250 OK - mail from <spamtest@test.com>
>>> RCPT TO:<securitytest%abuse.net@test.com>
<<< 250 OK - Recipient <securitytest%abuse.net@test.com>