Over the years, Twitter has changed their from address for notification e-mails as well as adding and removing helpful headers like X-Twitter headers. Is there a document somewhere that officially documents this that I can read for guidance?
The format and flavor of the emails should just be considered implementation details; they are authored with an intended human recipient. Any kind of programmatic interpretation of the emails is discouraged and would likely be better served through usage of the streaming API.
All I want to be able to do is categorize the e-mails into folders using something like procmail or to be able to process them from time to time using whatever your format is. I can make guesses based on observation, but I’d rather read some document that explains what your intentions are. Is it that hard for Twitter to write this down somewhere?