A custom script is the best way to accomplish this currently within Splunk.
See this previous thread -> http://splunk-base.splunk.com/answers/621/email-alert-subject
These may also be interesting:
http://splunk-base.splunk.com/apps/22368/php-scripted-alerts
http://splunk-base.splunk.com/apps/22398/use-javamail-for-scripted-alerts
http://splunk-base.splunk.com/apps/22397/use-python-mail-for-scripted-alerts
A custom script is the best way to accomplish this currently within Splunk.
See this previous thread -> http://splunk-base.splunk.com/answers/621/email-alert-subject
These may also be interesting:
http://splunk-base.splunk.com/apps/22368/php-scripted-alerts
http://splunk-base.splunk.com/apps/22398/use-javamail-for-scripted-alerts
http://splunk-base.splunk.com/apps/22397/use-python-mail-for-scripted-alerts
I have achieved this by adding a new line to the $SPLUNK_HOME/etc/apps/search/bin/sendemail.py file...but make sure you copy the file first in case it all goes wrong!