Mary Painter works for a company "marycompany" and access emails via their
own MS Exchange server, as usual.

Almost every time when Mary receives an external email and when she opens it
Outlook displays (as usual):
From: ...whoever
To: Painter, Mary
cc: ....
Subjec: whatever.,,
And then the Body message.

However, one day Mary received an email from another company "xyzCompany"
but her normal email address (Painter, Mary) was not displayed under the
"To:"

The name under "To" is generic - it read say "ABC, Accounts" (yes, there is
a comma.

I understand a little about putting together a few email-addresses and place
them under a group name (so that I can send the same email to a number of
persons). But I do a search in the Outlook "Global address List" at
"maryCompany" side but couldn't find anything to look like "ABC, Accounts".
Do I miss anything? I was about to conclude "ABC, Accounts" must be a
distribution list defined in xxxCompany rather than in "maryCompany". Can you
confirm me?

But is there a good way to tell what the distribution list is defined?

Jfc