Issue smpt server problems ssl certifcate from hostname not domain

[ChrisScottUK]

I am having a problem with smtp on domains in use on a server

I do not want to use smpt server as server.hostname.tld, but want to use is for each different domain as differentdomain1.tdl and differentdomain2.tdl etc etc

however in plesk 17.5 it means that differentdomain1.tld seeks the certificate of hostname.tld which is the mailserver and therefore fails with 'stream_socket_enable_crypto () peer certificate cn did not match expected CN' errors

How can I change the helo hostname for each differentdomain to the differentdomain so that the certificate used is the correct one?

 

[ChrisScottUK]

I've tried adding a let's encrypt certificate to mail@differentdomain1.tdl but still I get 'stream_socket_enable_crypto () peer certificate cn did not match expected CN' errors

All help really appreciated