exchange 2010

i am getting bounce back with error TLS_Srv:207.173.178.165 not found from recipients server.

I tried searching articles could not find any valid reason

207.173.178.165 is MX record for domain .

can you tell what is the reason

we are just ending emails from our exchange server through proofpoint gateway

attached please find the logs
C--Users-con-ccisat1pwk-Desktop-logs.txt
pramod1Asked:
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Wayne88Commented:
"Microsoft Exchange 2010 has a feature called 'Opportunistic TLS' which is enabled by default upon installation, this feature means Exchange 2010 will negotiate a secured SSL/TLS session wherever possible and encrypt the message.  By default SSL/TLS is not enabled on AuthSMTP accounts."

https://www.authsmtp.com/exchange-2010/exchange2010_SSL-TLS.html

You can disable it if you don't need it.
Adam BrownSr Solutions ArchitectCommented:
The mail server you're trying to send to isn't responding to port 25 requests on the address their MX record points to (Just tested it myself). Not much you can do about that other than try to contact them and let them know.
Wayne88Commented:
Odd, it seems fine to me.  Please see attached.
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pramod1Author Commented:
so waynee88

what is the problem at receipent server

is it SRV related or TLS related problem
Wayne88Commented:
It seems to me that the recipient's server doesn't support TLS so the fix are:

You can ask them to enable TLS or you can disable TLS at your Exchange.

Disable StartTLS on EX2010 Send Connectors - Quick Fix

Here is more info on the different encryption: SSL vs TLS vs STARTTLS
Adam BrownSr Solutions ArchitectCommented:
Do *not* disable STARTTLS on your server. That is a *terrible terrible terrible* idea. If you have Opportunistic TLS enabled, it will use TLS if the other side supports it, if the other side doesn't support it, Exchange will not use TLS. Some implementations of Sendmail break if there is a problem after TLS is negotiated. From what I can see in the logs, it appears that Proofpoint is using a Sendmail server for their mail transport and that is getting hung up in communication. The fix here isn't to disable STARTTLS on your Exchange server. The problem is Proofpoint's messaging servers or the other side's TLS configuration is faulty. Neither of these you can do much about without making phone calls. Alternatively, you can just try sending the message again.
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Wayne88Commented:
I agree with "If you have Opportunistic TLS enabled, it will use TLS if the other side supports it, if the other side doesn't support it, Exchange will not use TLS. "  I was simply pointing out the two possible solutions.

Let's go with option # 1, do the other side have it enabled?  If not, then maybe they should.  If faulty, then they should fix.
pramod1Author Commented:
but it is happening with number of domains now, it has been 6 or 7 now
Wayne88Commented:
What was wrong and the fix?
pramod1Author Commented:
we need to open a ticket with proofpoint one of their IP's is blacklisted and they are using send mail server as u suggested.

any further feedback from you will be appreciated

very good answer from you. thank you
Wayne88Commented:
Ok, great!  Glad you got narrowed down.  All the credit goes to acbrown2010.

acbrown2010, good troubleshooting!

cheers!
pramod1Author Commented:
cheers!!!
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