A default implementation-specific message is used. It contains at least the value of the "From" header field and the value of the "Subject".
The message data to be included in the notification. Implementations may shorten the message for technical or aesthetic reasons.
The server's default is normally the current user. You can override this, but in oder minimize/prevent forgery of the author value, the server implementations impose restrictions on what values can be specified.

Only few protocols support an importance or priority at all. Refer to the method's documentation for more details on how the importance is mapped.

Additional options passed to the mechanism as key and value pairs. Refer to the specific mechanisms for more details.

Specifies that a notification should be sent to a user. The format of the notification is implementation-defined and is affected by the notification method used.

The notification method is identified by a URI. For example, the notification method can be a tel URI [TEL-URI] with a phone number to send SMS messages to, or an XMPP [XMPP] URI containing an XMPP identifiers [XMPP-URI]. The supported notification methods are site-specific, but support for the [MailTo] method is guaranteed.

Sieve scripts should check the supported methods using the valid_notify_method test to be sure that they only use supported ones.