Relay via Sophos Central

prifesport Thank you for posting into the Sophos Community. I think we need to establish what Sophos products you are referring to first.  Do you have Sophos Email and you want it to handle outbound emails coming from a postfix email server instead of the Sophos Firewall's MTA?
Also what kind of "telnet and EHLO" test are you performing? And to which host name are you trying to use it on?
I got Sophos Email AND Sophos Firewall MTA in my home lab and the first thing that I can say as a behavior if your Postfix email server is behind the Sophos Firewall is that it intercepts any port 25.. So if you are trying to communicate with Sophos Email from the Postfix email server, the Sophos Firewall will answer in return instead of Sophos Email.
I think we need more overview information on this to assist you better. Thanks!

prifesport Thank you for posting into the Sophos Community. I think we need to establish what Sophos products you are referring to first.  Do you have Sophos Email and you want it to handle outbound emails coming from a postfix email server instead of the Sophos Firewall's MTA?
Also what kind of "telnet and EHLO" test are you performing? And to which host name are you trying to use it on?
I got Sophos Email AND Sophos Firewall MTA in my home lab and the first thing that I can say as a behavior if your Postfix email server is behind the Sophos Firewall is that it intercepts any port 25.. So if you are trying to communicate with Sophos Email from the Postfix email server, the Sophos Firewall will answer in return instead of Sophos Email.
I think we need more overview information on this to assist you better. Thanks!

I’m not sure that your home lab replicates a typical environment josepalad 

Stuart James  I'm not sure either :) Just trying to help.

Thank you for your support!

I was on vacation and therefore respond only now. Our hosted solutions have always used our Sophos XGS systems to send mail. However, since we switched to the Central Mail solution, these servers, which all have Postfix installed, now had to send via Central. If you use the right parameters in Postfix and build the envelope cleanly, so that Central can read the From cleanly from the Enevelop to assign the customer, then the whole thing works great! However, the systems with the Postfix installations are managed in another department, so I can not say which parameters are necessary. But maybe this info will help some who are looking for the answer: Postfix and Mailrelay via Sophos Central work in any case!