Problem:
You need to setup a shared mailbox as IMAP in Outlook 2016 (possible because you need to setup signatures for each account)
Solution:
- File > Account Settings > Account Settings
- New
- Shared Mailbox Email Address
- Under Advanced Options click on Let Me Set Up My Account Manually
- Connect
- IMAP
- Incoming: outlook.office365.com (Port 993, Encryption Method SSL/TLS)
- Outgoing: smtp.office365.com (Port 587, Encryption Method STARTTLS)
- Next
- Password: put in the password of the main user who has access to the Shared Mailbox
- In the prompt, put in the address of the main account followed by a slash with the shared alias name (mainuser@company.com/Shared)
- It’ll then reject the info you put in for the smtp server (smtp.office365.com), so delete the shared name (mainuser@company.com)