Exchange won't send to secondary MX

[cwhitmore]

We've had an issue sending email to another business that uses MessageLabs. All email sent from our Exchange 2010 server times out. If I manually telnet port 25 from my mail server to the primary MX for MessageLabs it times out, but if I telnet to the secondary MX it connects immediately.
Is there a reason why Exchange 2010 won't retry on the secondary MX?

 

[ShackDaddy]

Am I understanding correctly that your business uses MessageLabs too?

I may be wrong, but I think that the secondary MX is only tried if there is absolutely no listener on the primary MX, so if there is even a feeble attempt to answer the door at the primary MX, that would keep the process from failing over to the secondary.

For example, if the primary MX is finding your IP on a blacklist and is dropping the connections from your IP as soon as you attempt to connect, that might explain what you are seeing. If that were the case, I'm not sure why the secondary MX would allow the connection.

You have two choices here: you can create a custom Send connector for that domain that sends the mail directly to the IP of the working MX, or you can email MessageLabs and let them know that you are having an issue connecting to the first MX. I would just do the former.

Dave Shackelford
ThirdTier.net
TrainSignal.com

 

[cwhitmore]

Turns out MessageLags had us blacklisted. I had looked on mxtoolbox and did a blacklist scan there, but none from the list had us blacklisted.
MessageLabs support will not talk to the company getting blacklisted. You have to call the customer affected. Luckily they went ahead and made the change.