Under Exchange mailbox store there is no existent account name who is receiving and sending email without any errors.
Account was not hidden and was always working. Email client of this account works properly with Outlook 2007. Accounts listing in Exchange management snap-in does not contain his email record. We found that address book of other client does not display his name and tried to find his record to uncheck hidden but there was no any records in the list. How to find and fix this problem if no errors encountered with the delivery of his mail and replies back?