Hi Robertson,
Thanks for your help.
As for accessing Office 365 resources outside the corporate network, we would like to assign this privilege to only a select few employees. So it is fine for us to have a common mailbox, which the authorised admin would faciliate MFA for the select employees.
In other words, we do not bother about who accessed Office 365 is the primary account owner, since the access will anyway be granted by single authorised admin.
Please let me know if that is possible.
Regards,
Ganesan