We are migrating to a new domain. For that reason we are looking for a way to tell the people who still send mail to the old-addresses, that they will need to start using the new domain addresses.
Now we thought that sending a custom bounce would be the best deal. But how can we implement this? And is there a way to do this without having to edit the files directly? Or are there better ways to handle this issue?
For the record we don't want to use auto-reply.