How does a user log in to a delegated domain?
Users must use their fully qualified e-mail address as their login name. For example, if juser is a member of the delegated domain example.com, his login name would be his fully qualified email address, email@example.com. This login process pertains to all interfaces whether administrative, web-based or, any mail clients.
If the mail client does not allow the use of the embedded at (@) character, the precent (%) character may be substituted. The following will also be allowed: