I was doing update of Exchange Server 2010 today and got this error.

To resolve this issue, first I uninstalled Mailbox Server Role and restarted the server. Ran Setup.com /preparead and tried the installation but it failed again.

Their is one attribute in exchange for all the mailboxes, its homeMDB. I checked the attribute on the user account by going into Adsiedit.msc…Domain Partition…User…Firstname Lastname (your account) and found that it is set on the account.

Now there are two System Mailboxes from which this information is missing. Here is the attribute with homeMDB not set.

Now here is what I did to fix the issue. Go to Adsiedit.msc and Domain Partition and copy the attribute value from any user mailbox and paste it in homeMDB attribute.

After making the above changes, start the installation and installation will complete successfully. And, end result will look like this….

I hope it helps to someone, who’s running into the same kind of issue.