In order for any users to log in to email archiving software MailStore Server, a local 'MailStore' user account needs to exist.
You could simply just manually create users, entering usernames and passwords individually. However for any installation with more than a handful of users, as you can probably imagine, that can soon end up becoming a pain.
For this reason, MailStore includes the directory services feature to synchronise local accounts with an external user list which is what I'm going to cover in this post.