I'd like to extend this feature request slightly. We'd like to have parts of the template enforced, ie. a header/footer added to the user's message which should be configurable through sogo.conf. An example autoresponder message, consisting of a header, the user's message and a footer:

Automatic response on behalf of user {User Name from LDAP/mail address}:

Hi,

this is Joe. I'm writing my own user defined vacation message indication
I'm out of office. For urgent inquiries, please get in touch with Alice instead.

This message does not influence delivery of your electronic message.
You will not receive any additional automatic responses
on behalf of this user unless {n} days have passed.
--
Autoresponder Mailsystem Example Corp.

Some template variables like the number of days until the next automatic response and the user's name (preferred) or mail address (if resolving the name is too complicated) would be helpful.