Guide to CSS support in email clients : Designing an HTML email that renders consistently across the major email clients can be very time consuming. We've put together this guide to save you...
regex101 : Free PCRE-based regular expression debugger with real time explanation, error detection and highlighting.
Email Standards Project : The Email Standards Project is about working with email client developers and the design community to improve web standards support and accessibility ...
This page compares regular expressions that validate e-mail addresses in order to find the best one.
