SMTP Confusion

I have an i5 M15 running V7R1. Currently, when a user wants a download of
data from our i5, they run a menu option that collects the data they're
looking for and creates a CSV file in the IFS. This CSV file is then
emailed to them using SNDDST or SNDSMTPEMM. This process has worked fine
for a long time. We have our own internal email server (not on the i5) and
anyone who runs one of these processes is setup on the email server and
everything on the i5 (user profile and SMTP attributes) are setup to point
to the proper domain and email server.

About 1 1/2 years ago, the original owners sold the company to a large
international company. One of many changes we have been asked to make is to
move everyone from our internal email system to the corporate email system
(which is gmail based). This is a lower priority project and has not been
completed. In the mean time, I am not allowed to create any new email
addresses on the old email system, anyone new is assigned a corporate email
address.

The issue is that when a user with a corporate email address uses one of
the i5 processes that emails them a CSV file, they never receive it. The
email seems to be sent, according to the journals on the i5, but never
arrives in their corporate email inbox. I've spent a bit of time searching
the internet, but haven't seen anything yet that is helpful.

I'm wondering about the Mail Router option on the CHGSMTPA command. It is
currently set to our internal email server which is a different domain than
the corporate domain. Should I change this to *NONE? I've also read that
gmail filters incoming emails that have a gmail account as the sender, but
didn't originate from gmail (I'm not sure if this is true, or just
suspected).

Anyone have any thoughts? If more setting data is needed, just let me know.