Postfix and mixed case usernames

[John Francis]

I have just setup an FC4 box with Postfix and Dovecot for mail services.

I have two users on the box: userone and UserTwo (note the mixed case
in the latter).

Sending mail to userone works fine, but not so with UserTwo.

$ telnet mybox smtp
220 mybox.mydomain ESMTP Postfix
mail from: test at test.com
250 ok
rcpt to: userone
250 ok
quit

$ telnet mybox smtp
220 mybox.mydomain ESMTP Postfix
mail from: test at test.com
250 ok
rcpt to: UserTwo
550 <UserTwo>: Recipient address rejected: User unknown in local recipient table
quit

Postfix puts a message in maillog along the lines of "to=UserTwo,
status=bounced, unknown user (usertwo)".

Clearly a case(in)sensitivity issue.  Is there any way around this?

--
Kind regards,

John Francis