[Explain why it's bad idea. Always. Point to Friedl RE, link to REs, refer to Perl FAQ, and ...]
[Pertinent Perl stuff:
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Don Libes wrote "Authentication by Email Reception" [L2 ] to describe "use of email addresses as an authentication mechanism ... [which] provides reasonable security at very low cost ..."
tcllib / mime contains commands (mime::parseaddress, mostly) to parse email addresses.
But mime::parseaddress fails on simple, common cases. Specifically, it fails for some fairly typical user input:
[email protected],[email protected]
is OK but mime::parseaddress seems unable to deal with
[email protected] [email protected]
Then, when I try to stress it and send mail to
foo<>[email protected]
The parse "succeeds" but the send fails. -- CLN