Yes, Zammad would need to make available and use an optional separate “mail account field”.
For shared mailboxes the needed method is:
S = Shared Mailbox name, e.g. shared@example.tld
U = User who has full access to shared mailbox S, e.g. , e.g. bob@example.tld
- Get Access Token for User U.
- Open an IMAP connection using Username S, but access token obtained for User U in step 1
Taken from Access shared/delegate mailbox of Office 365 | Blog | Limilabs
Currently, Zammad uses user name U in step 1 and 2 with no way to change it in step 2.