[Dovecot] I need to enable percent hack in dovecot logins

I am using dovecot with vpopmail and qmail and problems is percent hack that works with qmail-pop3d does not work with dovecot.

So login works like that:

firstname.lastname%domain.ext I need that function to work with dovecot too, and I am using stable 0.99.x series of dovecot.

Problem is that some Apple machines client can't use at-symbol in their login names.

So, where I need to hack sources to convert % -> @ to get login working.

By default percent-hack does not work with dovecot. Any help?

Thanks.

-- Eero