Subject:
From:
Addresses: ...

Subject
The subject is used for any vacation response
Server's default Subject

From
Used to specify an alternate From address.
Address of the sieve script owner

Addresses
By default a response message is only send, if it was addressed to the recipient user or sieve script owner.
You can supply additional mail addresses. For Example if mails are forwarded or you have multiple aliases for a single mail address
Message Content Type
Instead of plaintext, the message can be a specified as a MIME Message
Is plaintext Message (Default)
Is MIME Message

Response Tracking
A vacation message is sent at most every some days to the same sender

Response Handles
The response tracking considers all vacation statements that use the same handle as the same response
The default handle considers subject, from, mime as well as the message. A custom handle can be any unique strings
Use default handle

The "vacation" action implements a vacation autoresponder similar to the vacation command available under many versions of Unix. Its purpose is to provide correspondents with notification that the user is away for an extended period of time and that they should not expect quick responses.

"Vacation" is used to respond to a message with another message. Vacation's messages are always addressed to the Return-Path address (that is, the envelope from address) of the message being responded to.