Possible fix for top-posting in Outlook

A list of regular expressions for tokenizing and parsing RFC822-compliant email addresses.

A collection of torture tests for MIME-compliant email readers.

A test of the portability of embedded images in HTML email across different popular (web) email clients. Note in particular the suggestion by Arjen van Reeven in the comments.

A sarcastic blog about the difficulties of parsing RFC 5322 email addresses. Note that the author seems to gloss over Folding Whitespace and Comments, and does not use a parser (generator) to tackle the problem.

" ... caff is a script that helps you in keysigning. It takes a list of keyids on the command line, fetches them from a keyserver and calls GnuPG so that you can sign it. It then mails each key to all its email addresses - only including the one UID that we send to in each mail. ... "