Ok. The steps would be roughly like shown below. When setting up, chose a restrictive filter for testing. I will send mails from my gmail account as a test until I am happy with the result. It is also useful to set polling to 5-10 seconds when you are testing to avoid having to wait a lot. Once you are happy with the result, change the filter, and set the polling to something less frequent, eg 60 seconds.
1) Create a job.
2) In the triggers tab, add an event trigger of type email. In the Conditions section, add the appropriate filters. For example: 'From address' contains @gmail.com. In the Actions tab, choose something like in the image. Note that you may not want to delete on Server! In the Save mail tab, chose to not save mails/attachments
We now have a job without any tasks, just a trigger
3) Send a testmail that passes the filter you have set. You will see that the 'Last run' columns changes if the trigger is activated.
4) Open the variables window. Find your job, choose triggers, Mail. You will find variables there with info from the last trigger.
5) Add a task that uses the email content. Pass to a .net method or whatever you want to.