I have recently setup an Exchange 2007 standard server for a client - it's been working perfectly for over 6 months. The client wanted to have separate address books between departments that cannot be accessed across departments. So I found some steps on how to separate the GAL without AD segregation here: http://www.msexchange.org/articles_tutorials/exchange-server-2007/migration-deployment/shared-hosting-exchange-2007-part1.html
First I followed the steps on my test environment and it worked perfectly and I was able to create separate GALs & separate mailbox DBs - so people in one GAL cannot see people in another GAL.
I implemented this on the live server yesterday and after testing it all worked. Today however no user can send e-mails they keep getting error "The operation failed. The messaging interfaces have returned an unknown error. If the problem persists, restart Out, cannot resolve recipient" I tried to recreate Outlook profile and configure exchange account and now no matter what account I use it says "your server or mailbox names cannot be resolved" and in outlook 2007 it says "The action cannot be completed. the name cannot be matched to a name on the address list." even though they are 100% correct.
I'm panicking as I cannot get in touch with the author of the article for guidance :-(
OWA still works perfectly though.... Please help