ALT Linux security policy defaults /var/spool/mail/`logname` user mailbox creation when a user added. Moreover, the mailbox created belongs to 'mail' group and is group readable and writeable.

Some mail software, e. g. Dovecot suite, may try to keep these attributes when using default mailbox as INBOX; this fails when the process is not belong to 'mail' group itself. Unfortunately, this is the default in ALT Linux.

One may disable mailbox creation by turning this control to 'none' state, or remove g+rw attributes from mailboxes (both in existing and future mailboxes) by turning this control to 'private' state. The last makes Dovecot happy about attributes keeping.