What should the correct are? Now there is 777 and I know that it's very stupid, but if I ask you before change them to prevent from permission error by time sending/receiving emails. Thank you.
Typical permissions for the directories the Maildir tree is 700. If you are sharing folders you need to allow 750 access to Maildir and 770 to shared folders. The share must be a member of the group that owns the Mailder and sub-folders. Files inside the directory should not have execute access. 600 is common; with 640 or 660 set for shared folders.
If the Maildir itself has 700 for its permissions, the subdirectories aren't as critical as other users won't be able to navigate to theme.
I've decide to seperate local storage and MTA and move all LDA functionality to the dovecot's
deliver. Main advantage is single uid/gid accessing mailboxes. Single dovecot config cover both LDA and POP/IMAP, that deal with dirs/files. No file permission section in the MTA config at all.