Why did my migrated mailbox disappear?

If a mailbox doesn't show up in the Exchange Control Panel after a migration, some simple factors could make it look like it went missing.

So I have just finished an Exchange 2003 to Exchange 2010 migration, and then did an Exchange 2010 to Exchange...

2013 migration. Everything except for public folders seemed to go smoothly, but now I have one mailbox that doesn't show up in the Exchange Control Panel. If I run a Get-Mailbox command, the migrated mailbox shows up but isn't in the webmail console. Anyone see anything like this before?

It isn't uncommon to hear public folder complaints during migrations. It sounds like you were able to complete that process even though you had difficulty, so I won't rub salt in that wound.

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I'm fascinated by the issue of the disappearing migrated mailbox from the new Exchange Admin Center (EAC). It's interesting that it's a functioning mailbox visible from the Exchange Management Shell (EMS) but not the EAC, especially considering that the EAC is essentially a Web-based script-building tool for the EMS.

I've seen some interesting issues with migrated mailboxes from my experience with completing migrations over the years, so I have some thoughts as to what the possible cause could be. In Exchange Server 2013, the default view in the EAC for recipients is Mailboxes. It uses a custom filter to display only mailboxes with the "Mailbox Type" of "User." If the mailbox in question has a recipient type other than User, it wouldn't be visible under mailboxes. Just a few tabs over to the right, there's one tab called Shared. You may find the missing mailbox in this tab.

Migrations often expose issues we didn't realize existed. For example, it's possible this migrated mailbox had a cocktail of permissions, causing the migration to convert the mailbox to a "Shared" mailbox in an attempt to preserve permissions. When this happens, there are often a few more mailboxes behaving the same way, making the issue easier to identify. It may have been this one mailbox in your case.

You can run Get-MailboxPermissions <mailboxname> to see what "AccessRights" are assigned to the NT Authority\Self user on the mailbox. A regular account should have FullAccess and Read Permissions. If it has ExternalAccount as well for an AccessRight, that could be the issue. If this turns out to be the issue, there's an easy enough fix documented in the TechNet article "Convert a Mailbox."

About the author:
Richard Luckett is a consultant and instructor specializing in messaging and unified communications. He's been a certified professional with Microsoft since 1996 and has 20 years of experience in the public and private sectors. He's a Microsoft Certified Trainer with more than 15 years of training experience with the Microsoft product line and received the Exchange MVP award in 2006, 2007 and 2008. He's also an expert in deploying and integrating Exchange Server and Lync Server. He leads the Microsoft training and consulting practice at LITSG.

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