cyrus-imapd and dovecot

[Marcos-Fedora Brazil]

Hi

I am using FC3 with dovecot to pop3 users... but occurs errors in webmail 
login ( uebimiau.sourceforge.net ) when mailboxes are big....
now I was installed cyrus-imapd, but when I login, in pop3, cyrus does not 
authenticate, it fail... I looking for a way to config cyrus to authenticate 
via passwd/shadow or sql, but in sql I think is difficult, because sendmail 
does not have support to sql

Thanks

Marcos