When sending an e-mail via Outlook to a recipient in the same domain, the following error is thrown:
"E-mail address you entered could not be found"
E-mails to users from other domains are sent fine.
Outlook client has been configured in Cache mode. Therefore, when something is changed it Distribution List, the changes may not be immediately applied to the local clients.
Update the OAB on Exchange server using Exchange Management Console:
Update-OfflineAddressBook -Identity "<name of the OAB>"
Then try removing .OAB and .n2k files in local Outlook folder, which is typically:
%USERPROFILE%\Local Settings\Application Data\Microsoft\Outlook
Download the address book in Outlook through Send and Receive > Download Address Book.
Setup the local Outlook profile anew.
When lots of users should be updated and you have not access to all of them - Create new Distribution List with same name and new alias in Exchange Management Console. In case of lack of access to local clients and if there are a lot of users that receive this error, provider may create a new Distribution List with the same name and a new alias through Exchange Management Console