How to extract the email address from the From: header?

[Marcin Borkowski]

Hi list,

"From" headers (or "To" ones, for that matter) are sometimes plain email
addresses and sometimes strings of the form "Real Name
<email@add.ress>".  I could write a function (or maybe even a regex) to
extract the email part in the latter case, but Emacs being Emacs, I'm
pretty sure something like that already exists.  Am I right?

TIA,

-- 
Marcin Borkowski
http://octd.wmi.amu.edu.pl/en/Marcin_Borkowski
Adam Mickiewicz University