On 6.1.2012, at 18.37, mailinglist wrote:

Installed dovcot from Debian .deb file. Creating a new account for system users sets permission for user-only. Where to change initial permissions on creation of mail folder and other subdirectories.

Permissions for folders are taken from the mail root directory. http://wiki2.dovecot.org/SharedMailboxes/Permissions has details.

Permissions for newly created mail root directory are always 0700. If you want something else, create the mail directory with wanted permissions at the same time as you create the user.

Installed dovecot using "apt-get install dovecot-imapd dovecot-pop3d". Any time when I create a new account in my mail client for a system user, Dovecot tries to create ~/mail/.imap/INBOX. The permissions for mail and .imap are set to 0700. By this permissions INBOX can not be created leading to an error message in log files. When I manualy change the permissions to 0770, INBOX is created

I don't really understand why INBOX couldn't be created. 0700 should be enough for most installations. Unless you have a very good reason you shouldn't use 0770 for mails (sounds more like you've a weirdly configured mail setup).