I have tried setting Google for SMTP both via the "Google Apps or Gmail" and "Custom SMTP" options.
In both situations, if I "Run Self Test", the email has a message ID like 58d9c41e.4463620a.f9604.a62f@mx.google.com.
Regular order confirmations or "Send Email", however, have a message ID like 20170328020401.EF1036073F@[our server FQDN].
For the time being, I have configured Postfix to relay the emails via Google but would prefer not to be overriding all emails sent from the server like that.
I have tried setting Google for SMTP both via the "Google Apps or Gmail" and "Custom SMTP" options.
In both situations, if I "Run Self Test", the email has a message ID like 58d9c41e.4463620a.f9604.a62f@mx.google.com.
Regular order confirmations or "Send Email", however, have a message ID like 20170328020401.EF1036073F@[our server FQDN].
For the time being, I have configured Postfix to relay the emails via Google but would prefer not to be overriding all emails sent from the server like that.