Administrator accounts are denied access to services such as IMAP, however, the administrator can still log in to WebConfig.
For stability purposes, a user is allowed team membership to no more than 1023 teams. When a user account is created, an invisible team is also created, using the same name. Administrators on a server are automatically granted membership to all teams and users. Therefore, if the total number of teams and users is greater than 1023, administrators will be denied access to network services. The administrator account may still perform all administrative WebConfig responsibilities.
Resolving the problem
Administrative accounts are recommended solely for the purpose of administration, rather than for everyday usage.
This recommendation provides a more secure administrative environment and will also avoid the problems of needing to authenticate to the services, because the account is used purely for administrative purposes.