No validation routine for an os.path

[Roger Binns]

Edward Diener wrote:
> I do not totally agree, especially as the OS will know whether
> something is valid so it obviously has rules itself. But I grant it
> is more difficult than might be assumed. BTW email addresses actually
> do have a format which can be parsed ( RFC 822 originally ), although
> again it is complicated.

I don't think Peter meant whether or not you can extract an email
address, but rather if it is actually valid.  For example,
which of these are valid?

   john at example.com
   foobar at nosuchdomain.com
   fred!foovax!kremvax!nasa
   one at two@three.com

As a bonus question, are email addresses case sensitive?

Roger