[Dovecot] why dovecot try to access the uses's home?

hi, after i try to use dovecot with ldap i configure dovecot as:

first_valid_uid = 499 last_valid_uid = 499 first_valid_gid = 499 last_valid_gid = 499 default_mail_env = maildir:/home/mail/%d/%n auth_userdb = static uid=499 gid=499 home=/home/users/%d/%n auth_passdb = ldap /etc/dovecot-ldap.conf

but after this i've got the error in imap.log:

dovecot: Dec 29 14:39:14 Fatal: chdir(/home/users/<username>) failed with uid 499: Permission denied

i see the reason since each user has it's own uid and uid 499 can't access to the users home which has 0700 access right. but why dovecot would like to access the user's home? does it nessesary? since in this case one static uid can be usable or this uid has to be read (write?) access to all user's home. is there any usage of static uid in this case? yours.

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