Hi, I have a problem with my running exchange 2007 server. It has been running without problems for a few months. But recently, Users have been getting problems when using Outlook (OWA works fine) The problem is that the exchange server keeps asking them to enter their username and password, Sometimes the enter it and the exchange server refuses it but sometimes it works to change the format that they enter the username (f.x. john@contoso, contoso\john, or their direct email address john@mail.com) We have a single domain, But alot of accepted domains for the exchange server for multiple companies that exist within our organization. All the users are logged in to a domain user and that user has the exchange mailbox. So it's not like they are logged in with one user and checking the mail for another user. Any ideas ? Any help would be really really helpful.

Are you auditing security on the exchange server? If so, what types of logon failures are you seeing? Also, are you using rpc/https ? If so the logon name should always be the UPN.