Since last week, we have had two users who were disabled in Active Directory need to be re-enabled. They are able to log onto their computer just fine, but they cannot open their mailbox with either Outlook 2013 or OWA. When I look at the mailbox in the Exchange Admin Center, the Mailbox Usage tab shows the warning: "The user hasn't logged on to mailbox <name of domain/ou/user ('mailbox ID, I'm guessing')>, so there is no data to return. After the user logs on, this warning will no longer appear." This makes it sound like the mailbox was re-created, but I know the mailbox has been used before the account had been disabled. Further, when I click on Mailbox Features, I get this warning: "Cannot open mailbox /o=Organization Name/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Configuration/cn=Servers/cn=SERVERNAME/cn=Microsoft System Attendant." With one of the two affected users, I just re-created the entire account, but I don't want to have to do that with every user we disable. We haven't had this problem in the past, and I haven't made any changes aside from Windows Updates. I appreciate any insight you can provide.