OT: Postfix works on test server, silently fails on live server

This is a bit off topic, as it’s more a Postfix question than an RT one. On
my test server, I have Postfix working beautifully, sending mail via Gmail.
Yet, on the live server we so recently switched to, I’m having a problem
getting mail to send. The strangest part is that the mail log shows the
mail was “delivered”, yet it never appears at its destination. It’s not
even in the sent folder of the Gmail account in use. I simply copied the
main.cf file from one server to the other, made the sasl_password file and
mapped it, and restarted Postfix. Is there more to configuring Postfix that
I may have skipped on the new server in trying to pull over an existing
configuration? Any other obvious steps I should try? I’m on Debian 8.5 and
installed using apt-get. Thanks!

Alex Hall
Automatic Distributors, IT department