Hi,
As internal Zammad users in most cases identified by e-mail, it would be great to have an ability to authenticte them through mail server.
E.g. Zammad is used as an internal HelpDesk system for employees. Employees write mails to create new tickets and get notifications with the link to their tickets in Zammad. They open this link, enter their e-mail as a login and mail passwords. These credentials are verified by company’s SMTP/POP3/IMAP server granting user an acces in case of successfull authentication.