[MAXOB]

Рыская по дебрям интернета нашел следующую информацию:
IMAP LOGINDISABLED capability

The current IMAP protocol specification (RFC 2060) requires the
implementation of the LOGIN command which uses clear-text passwords.
Many sites may choose to disable this command unless encryption is
active for security reasons. An IMAP server MAY advertise that the
LOGIN command is disabled by including the LOGINDISABLED capability
in the capability response. Such a server will respond with a tagged
"NO" response to any attempt to use the LOGIN command.

An IMAP server which implements STARTTLS MUST implement support for
the LOGINDISABLED capability on unencrypted connections.

An IMAP client which complies with this specification MUST NOT issue
the LOGIN command if this capability is present.


Read more: http://www.faqs.org/rfcs/rfc2595.html

Непонятно теперь только одно, КАК это отключить?