Exchange: Shared Mailbox is not able to open in Outlook (with Full Access permissions) or in OWA

A Shared mailbox is not show up in Outlook or not able to open in OWA, and it gives this error in OWA:

“Your Account has been disabled”

Do not check the Active Directory Account. It is nothing to do with the user account. Error message means OWA is disabled on the mailbox.

Solution:

Exchange Admin Console:

• Find the mailbox and click to select
• On the right-side pane, find Outlook on the Web under Email Connectivity.
• Enable the OWA
• Open Mailbox Properties and select Mailbox Features
• Find and enable MAPI

Exchange Admin Shell:

Set-CASMailbox <Mailbox Alias> -OWAEnabled:$true -MapiEnabled:$true

If you run this command, OWAEnabled should show True:

E:\ Get-CASMailbox SharedMailbox@company.com 
Name ActiveSyncEnabled OWAEnabled PopEnabled ImapEnabled MapiEnabled SmtpClientAuthenticationDisabled
---- ----------------- ---------- ---------- ----------- ----------- --------------------------------
offers True True False False False