Sometimes you need mail adresses and postboxes that need to be accessed by multiple persons. In a company for example there could be a mailbox firstname.lastname@example.org and if you are planning for example a wedding it can be a good idea to have an account email@example.com that can be accessed by you and yor (future) wife. It is definitly not the best idea to create a “normal” account and just give the password to all people who might need it. This might leed to confusion (and data loss). In my opinion accounts should always be bound to a person.
The solution for my LDA (aka mailserver) dovecot is called “SharedMailboxes”, ie mailboxes that are shared between users and linked to their accounts. It wasn’t that easy to setup but finally I could get it to work in the following way:
The content however is old and might be outdated.