Any way to make a shared mailbox(not a shared folder)

Hello I wonder if there is a right way to make a shared mailbox? I do not mean "shared folder" but a whole mailbox. E.g. I have a mailbox info@company.com and I have a user mailbox user1@company.com. I would like that a user which can already authenticate as user1@company.com can setup another account in his Thunderbird as, say, user1@company.com\info@company.com or something like user1*info, enters his own password and can use the mailbox info@company.com as his second mailbox. It might be something similar to master user feature but I do not want the user1@company.com to have access to all the mailboxes on the dovecot imap server.

-- Regards Maksim Rodin