The IMAS/CAD does not support posting to the Twitter feed by itself.
You will need a 3rd party to facilitate the process. Any 3rd party app that will take an email and turn it into a Twitter feed will work.
A few that I can think of are:
ittt.com and twittermail.com
Each has it's own way of handling the email sent to them, you will need to follow their directions on how to make it work.