For some reason we are all the sudden started getting complaints from people trying to email our company. All of the rejected emails look like this:
There was a SMTP communication problem with the recipient's email server. Please contact your system administrator. <email address> #5.5.0 smtp; 500 syntax error, command unrecognized>
We are running a watchguard firewall that runs SMTP proxy service. On this I have to where it allows all traffic and attachment to come through. NO RESTRICTIONS @ this time. Can someone help me with this error. I have researched it but I don't find any specific answers as to why some emails coming in work and some don't.
