[Dovecot] Problem with IMAP and MAIL environment

Here is the problem:

Jul 19 10:40:17 mail1 pop3(master): mbox: Can't create root IMAP folder /home/usuarios/master/mail: Permission denied Jul 19 10:40:17 mail1 pop3(master): MAIL environment missing and autodetection failed (home /home/usuarios/master) Jul 19 10:40:17 mail1 dovecot: child 3528 (pop3) returned error 89

Is there anyway to avoid it? Thanks.