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The previous regex ` ^[\w\.\+\-]+\@[\w]+\.[a-z]{2,3}$ ` matched only a small subset of valid e-mail address (e.g.: didn't match domain names longer than 3 chars or user@this-domain.de or user@multiple.level.dom) and needed to be with start (^) and end ($).
This ` [a-zA-Z0-9!#$%&'*+\/=?^_`{|}~-]+(?:\.[a-zA-Z0-9!#$%&'*+\/=?^_`{|}~-]+)*@(?:[a-zA-Z0-9](?:[a-zA-Z0-9-]*[a-zA-Z0-9])?\.)+[a-zA-Z0-9](?:[a-zA-Z0-9-]*[a-zA-Z0-9])? ` is not perfect (e.g: can't match oriental chars), but imho is much more complete.
Regex tested with several e-mail addresses with Python 3.6.4 and Python 2.7.14 on Linux 4.14.
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