I would like to set up Exchange so that when a user (e.g. firstname.lastname@example.org) sends an email to somedomain.com Exchange makes the email appear to have come from email@example.com.
This would have to be done on a per-domain basis, and invisibly to the user. So all emails come from firstname.lastname@example.org, except emails to somedomain.com, which appear to come from email@example.com.
If anyone has any ideas I would really appreciate it.