I'm currently involved in researching security problems and how perimeter firewalls might help mitigating them. During the research I've found several ways to evade existing IDS, firewalls and other security systems at the application level by using interpretation differences between the protecting and the protected system (i.e firewall and client).

This research looks into TLS support for mail delivery to the Alexa top 1M domains, especially at how many sites support TLS, supported protocol versions and ciphers and typical setup or implementation errors which might hinder the delivery of mail.

In this article I provide tips for debugging SSL/TLS-problems and show typical and less common problems and how to solve them.