I need to codify it as it's just notes and numbers scattered across experiments for now, but it's something I plan to do as I want to blog about each example (along with all of the other weird things I've learnt in the e-mail business so far).

I realized I should add a note, however, that everything I've said only applies to bulk e-mail (and sent through systems with a reputation for such) and not transactional or manual e-mail which suffers from fewer oddities for obvious reasons.

You think spammers aren't going to read it too?