Roles That Can Post
This allows you to grant access to other users to post via email if they have the proper access level. Administrators can always post.
Put each email address on a single line. Posts from emails in this list will be treated as if they came from the admin. If you would prefer to have users post under their own name – create a WordPress user with the correct access level.
This will be the poster if you allow posting from emails that are not a registered blog user.
Force User Login
Changing this to yes will cause Postie to try and login as the ‘from’ user if they exist. This should be set to ‘Yes’ if you use custom taxonomies in the subject line.
Allow Anyone To Post Via Email
Changing this to yes is not recommended – anything that gets sent in will automatically be posted.