SOLVED: How To Setup a Shared Mailbox in Microsoft 365 Exchange Server

There are many reasons you may want to setup a shared mailbox, but the one we see the most often has to do with licensing.  Shared Mailboxes in Microsoft 365 do NOT require a license, although all users that connect to that shared mailbox DO require a license.

Note that a Exchange Online Kiosk License is insufficient to access a Microsoft Office 365 Shared Mailbox; you need a full license.

Also, there are many that will tell you it is not possible to log into a Shared Mailbox directly, but we will show you how to easily get around that.

1. Access the Microsoft 365 Exchange Admin Portal
   1. Surf to portal.office.com, sign in, click the A icon for the ADMIN portal on the left rail
   2. Click SHOW ALL… (in the left menu) then click EXCHANGE
      Alternately you can surf directly to admin.exchange.microsoft.com 
2. Expand RECIPIENTS
3. Click MAILBOXES
4. Click ADD A SHARED MAILBOX
5. Enter the DISPLAY NAME, EMAIL ADDRESS and ALIAS you want
6. Click the SAVE button
7. Click on the Shared Mail box you just created
8. Click MANAGE MAILBOX DELEGATION
9. Click EDIT on both READ AND MANAGE and SEND AS and add whoever you want to have access to that account

If you want to access a Shared Mailbox directly using Outlook or Outlook Webapp, you need to assign it an Exchange license.

If you want to use a Shared Mailbox as an SMTP relay (i.e. you want a program like phpBB to send email through them) you can’t.  See this Microsoft thread on Authenticated SMTP with Shared Mailboxes.