Postfix and mixed case usernames

[John Francis]

On 19/01/06, Tim <ignored_mailbox at yahoo.com.au> wrote:
> On Thu, 2006-01-19 at 19:18 +1100, John Francis wrote:
> > 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.
>
> There are warnings against doing such things (using capital letters in
> mail addresses), and for good reason.  You've struck one problem, how
> many more do you want to have to solve?  Your best solution is to stop
> wanting do to that.
>

I've only ever used lcase usernames myself out of habit.  Also, in
this case it will be quite easy for me to get the usernames changed. 
But the question still remains: why should it be a problem?

I understand that the domain part of an email address should be case
insensitive, but where does it say that about the local-part?  In
fact, RFC 2821 states that the local-part should be treated as case
sensitive.

Most MTAs don't strictly enforce this and try to treat the local-part
case insensitively.  This means that whether I send it to usertwo or
UserTwo or USERTwo, it should (by convention, in non-compliance with
the RFC) go to the same mailbox.

It appears that this is in fact what happens in Postfix.  To avoid
confusion it just lcases the local-part and attempts delivery.

Hmm... I think I've just answered my own question.  For Postfix to be
able to deliver in the case where the mailbox name is UserTwo and is a
Unix account, it would first need to look for a match with every
combination of each character in ucase an lcase.  Not very practical.

This is an issue with Unix accounts because usernames are
case-sensitive, but I whether that is the case with Cyrus-IMAPd.

--
Kind regards,

John Francis