Exchange Configuration
USER EMAIL: user@maindomain.com
PASSWORD: password
SHARED MAILBOX: shared@anotherdomain.com (could also be @domain.com, of course)
SHARED MAILBOX ALIAS: shared-mailbox
Note: Please make sure to create the UNIQUE alias always with the mailbox, because it creates the user [alias]@maindomain.com. In this case shared-mailbox@maindomain.com
Settings for IMAP Configuration
EMAIL ADDRESS: shared@anotherdomain.com (shared mailbox)
IMAP SERVER: outlook.office365.com
SMTP SERVER: smtp.office365.com
USERNAME: user@maindomain.com\shared-mailbox (user\shared mailbox alias)
PASSWORD: password (user's password)
SMTP Login Is Different
USERNAME: user@maindomain.com (users email)
PASSWORD: password (user's password)