I have looked all over in here for answers to issues related to this problem. I have tried all the answers that people suggested....
This is the issue....
There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.
<nwex0.ideas.ad #5.5.0 smtp;500 Syntax error, command unrecognized>
We have a Watchguard Firebox 1000 as our firewall, we have two exchange servers that communicate with eachother so disabling the ESMTP verbs i do not think is an option, as the two exchange boxes would not communicate.
This error is sporadic, mostly happens when emailing hotmail, but has since been erroring out when communicating with other email addresses as well.
I have checked the blacklists to see if we are blacklisted, our exchange server IP is 22.214.171.124, we are not on any blacklists.
Please help as have limited knkowledge, but will try what you suggest.