I'm about to register for the service and give it a try. In case it is of no use for me, is there an option to delete my account and have my personal data removed from your system?
Yes. Canceling your account is an easy and no-questions-asked process. It's done online, right from the user private area:
When cancelling your account, we will delete all emails and files stored by us as part of your Evidence license conditions, as well as your personal information. However, we commit ourselves to never remove the log records for your registered emails. If you ever need to confirm the integrity of an email or file, let us know.