Today i have a user that could get access to the exchange webmail. (OWA).

There are som solutions for this error, try to fix from bullet number 1, and down.

1. Get-Mailbox User_Name | format-list ExchangeVersion
   if the version is below 0.1 the run this command:
   Set-Mailbox User_Name -ApplyMandatoryProperties
2. 1. Open ADUC, and go to the properties of the user that is having problems.
   2. Click the Security tab, and then the Advanced button.
   3. Make sure the “Allow inheritable permissions from the parent to propagate to this object…” is checked.
   4. Give AD time to replicate the change and try to login in via OWA again.
3. Restart the Information Store service.
4. 1. Open ADUC, and go to the properties of the user that is having problems.
   2. Click the Security tab, and then the find the account SELF.
   3. Give it fuld access.
   4. Give AD time to replicate the change and try to login in via OWA again.
5. If all this dosen’t work, disable the user in Exchange EMC, this will delete the mailbox, so remember to have a backup of the account first. Then create a new mailbox to this user, and create the user again, and restore the mailbox from your backup.