[Nottingham] emails containing spaces

Nick Leverton nick at leverton.org
Tue Oct 16 19:15:37 UTC 2012

On Tue, Oct 16, 2012 at 03:13:54PM +0100, Jason Irwin wrote:

> This is a good article on the topic:
> http://www.regular-expressions.info/email.html
> Even if you don't plan to use RegEx, it walks through the pitfalls.
> Strictly speaking addresses are case sensitive, but the de facto
> standard today is to be insensitive (thank you, Exchange).

Strictly strictly speaking, the Right Hand Side is case insensitive,
but the Left Hand Side may be case sensitive or insensitive depending on
the recipient system - this has always been so.  Even before Microsoft
learnt how to spell "PC", before the book familiarly known as "!%@::" was
published, RFC 821 said "For some hosts the user name is case sensitive,
and SMTP implementations must take case to preserve the case of user names
as they appear in mailbox arguments" - the implication even then being
that most were insensitive.  This was quite important when trying to route
your mail to and through the various weird inter-network mail gateways.

> More the gory details are in RFC-2822 if you feel brave.

RFC 5322 these days :-)

> Personally I tend not to do heavy validation of email addresses and the
> number of sites that try to be "clever" and trip themselves up by not
> accepting basic things like "-" or "+" in the local part would be
> hilarious, if it wasn't so depressing.
> This mini-rant makes me want to start a "yer doin' it wrong" web site
> where I publicly ridicule companies that can't get basic things like
> this correct.

You could take over rfc-ignorant.org, I hear they've given up the struggle
themselves ;-)


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