There has been many questions/requests for better (=configurable templates) email alerts but has anyone actually published anything beyond quick hacks of sendmail.py or is this already on roadmap of some Splunk release ?
Here is one of the best examples of such feature requests.
Splunk have listened.
Version 6.1 of splunk now has TO: CC: & BCC:, Priority, Subject and a multi line Message.
You also have the option of including the search string or not as well as the results.
And they have listed the tokens (like $alert.severity$) that can be used.
And this can be triggered from the search string with the sendmail command.
See http://docs.splunk.com/Documentation/Splunk/6.1.2/Alert/Setupalertactions#Email_notification for details.