I recently was asked how to connect a shared mailbox via IMAP to an Outlook client now this isn’t standard behavior or common practice as only a licensed user should access a mailbox. Now I know there are many resources online and suggestions out there but I am aiming to clear this one up using an Outlook 2016 client which does work with Office 365!
First of all create a shared mailbox, in this instance we are using shared@adam-hand.com. Then give full permissions as you normally would for a licensed account in this instance adam@adam-hand.com.
- Open up the profile manager on Outlook
- Add a new profile, and give it a name
- Select “connect to a different account” in the bottom right hand corner
- Select “Manual setup or additional server types
- Select POP or IMAP
- Fill out the following information
- Your Name – What ever you want
- Email address – shared@adam-hand.com
- Account Type – IMAP
- Incoming mail server – outlook.office365.com
- Outgoing mail server – smtp.office365.com
- User name – adam@adam-hand.com\shared@adam-hand.com
- Password – The password for adam@adam-hand.com
- Tick the box for remember password
- Select the more settings button
- Under the Outgoing Server tab select “My outgoing server (SMTP) requires authentication” and “Use same settings as my incoming mail server”
- Select the Advanced tab
- Under incoming server IMAP enter – 993 and SSL/TLS
- Under Outgoing server (SMTP) enter – 587 and STARTTLS
- Select Ok
- Then Next and the test should pass successfully and you are good to go.
ahandyblog 
Hi there, I’m trying to get this running in offlineimap but I’m hitting an authentication error. I’m wondering if it still works for you in 2020?
Hi Daniel – I haven’t tried for a while as I haven’t seen many people using this method anymore. I will have a look and let you know.
Hi Andy, thank you but in the end my IT department pointed me in a direction which worked for me.
With a personal Outlook email of daniel@institution.com and a shared Outlook address of group@institution.com, the IMAP username field would simply need to be formatted daniel@institution.com\group
Ie no @domain.com at the end of the group.
As for sending via SMTP, it’s simply the username, daniel@institution.com
Seems to work fine with using offlineimap, emacs and mu4e.
I mean Adam not Andy! Sorry!
no worries and thanks for your information which is now updated in my article
Hi,
Before using this tips with an exotic client,
I have tested it with a tiny IMAP client (http://www.ch-software.de/popman/) …
it doesn’t look to work.
It does not work in Outlook. Even if I use a username like “adam@adam-hand.com\shared@adam-hand.com”, I get the main mailbox content, that is “adam@adam-hand.com” inbox content rather than “shared@adam-hand.com” inbox content.
Thanks and sorry for the late reply I have just posted an update to this article and it does indeed still work,
Hi Adam Hand,
Thank you very much for the solution.
Unfortunately I am authentication error. I have a question. Is this works on a non Licensed Shared Mailbox?
Hi Sebastian I can confirm this works on a non licensed shared mailbox which was how I did the test. I was using the latest version of outlook using office pro plus from office 365 as the client as well.