Right .. I had a quick look and found two articles of exim3 age and one weblog on mail forwarding. Neither of which suited my needs.

I have exim4 toodling along quite happily accepting mail from outside and sending mail from registered users. I now want to do something slightly different.

Let's look at user1@example.com and user2@example.com.

user1 is, if you like, declared to the system - she's in the /etc/passwd and /etc/groups file and she can log in and use mutt to look at her mail.

user2 isn't declared to the system, has no log in capability but wants mail coming from his contact form, hosted on my web server, to go to a specific email address on another domain, e.g. fred@example99.com.

I had planned to use example2@example .com and then reroute the form mail.
So I set up example2@example.com : fred@example99.comin the /etc/aliases file.
and, as it didn't work the first time, restarted the mail server to see if it would work then.

It doesn't work.

In the exim4 log I get example2@example.com as an unrouteable address.

Is there a way to achieve this without registering user2 on the system?

What is wrong with this textarea?
Debian stable with IceWeasel - if I type enough to require a scroll bar then it doesn't appear.
Navigating through any text using the up and down arrows produces variable results.
Where's the clues for actually making a successful post?