in
Please frame the question for me to ask
"And what did the mail admin at your company say regarding this behavior
that they configured for off-network access to their mail host?"
mail admin
Whomever administers your company's mail server.
your company
Whatever is the company whose mail server you are trying to use. The
place you called "office".
this behavior
What you described happens when at home and trying to use your company's
mail server from there.
off-network access
You are at home. The mail server is in the company's network. At home,
you are not in the company's network (although it can be emulated via
VPN).
their mail host
The mail server at the "office" that you are trying to use.
A simpler response:
Ask the admin of the mail host that you are using.