Exim: Only Root Getting Messages

[Lord_Override]

I managed to get exim working (although I have no idea how) with fetchmail and I can send messages to the superuser root and they're received but if I try to send them to user@debian (debian is my hostname) I get a message back saying they undeliverable because the user @ debian was not found. What can I do? Is there something special I need to do to enable users to access mail sent to them?

[Lord_Override]

I figured it out, its because the username started with an uppercase character, it won't send if it does! Is this a bug?

[nuisance]

No, almost everything on a Linux system is case-sensitive.

[Lord_Override]

I know but the username does start with a capital letter when I added it: User and I mailed to is User@debian which was rejected despite the case being correct for the user.