Mishandled underscores in usernames

[Kevin Podsiadlik]

Are there some email programs out there that can't handle the
underscore character in a username properly? I ask because I have,
over the years and even still today, gotten quite a bit of misdirected
non-spam email to an account I own at x...@yahoo.com, that was intended
for xxx_y...@yahoo.com. I'd like to be able to give some standard
advice (like "stop using that program" or "upgrade to version
such-and-such") to people whose emails keep getting misdirected in that
fashion.

[Mark Crispin]

On Thu, 19 Jan 2006, Kevin Podsiadlik wrote:
> Are there some email programs out there that can't handle the
> underscore character in a username properly?

I'm not surprised. There are plenty of programs (especially f*cking web
forms) which are under the misconception that "+" is not a valid character
in an email address. Why shouldn't "_" enjoy the fun.

In fact, "_" is not valid in domain names, so it should never appear in
the part to the right of the "@". It's perfectly valid in the part to the
right of the "@".

The following characters are all valid in email addresses:
all 52 upper and lower-case alphabets
all digits
any of these: ! # $ % & ' * + - / = ? ^ _ ` { | } ~
. is also permitted if it is not the first or last character
using quoted strings, anything else except for NUL, CR, and LF

-- Mark --

http://panda.com/mrc
Democracy is two wolves and a sheep deciding what to eat for lunch.
Liberty is a well-armed sheep contesting the vote.

[ynotssor]

"Mark Crispin" <m...@CAC.Washington.EDU> wrote in message
news:Pine.OSX.4.64.0...@pangtzu.panda.com

> In fact, "_" is not valid in domain names, so it should never appear
> in the part to the right of the "@". It's perfectly valid in the
> part to the right of the "@".

One presumes 's/right/left/2'

[Alan Clifford]

On Thu, 19 Jan 2006, Mark Crispin wrote:

MC> I'm not surprised. There are plenty of programs (especially f*cking web
MC> forms) which are under the misconception that "+" is not a valid character
MC> in an email address. Why shouldn't "_" enjoy the fun.
MC>

The usual "you have entered an invalid email address" telling off is very
irritating but Amex seem to have a new way of not accepting myname+amex@,
viz.

"WE'RE SORRY...

Unfortunately our system does not seem to be working at the moment, please
try again later.
We are sorry for any trouble this has caused you."

--
Alan

( If replying by mail, please note that all "sardines" are canned.
There is also a password autoresponder but, unless this a very
old message, a "tuna" will swim right through. )

[dav...@alpha2.mdx.ac.uk]

In article <Pine.OSX.4.64.0...@pangtzu.panda.com>, Mark Crispin <m...@CAC.Washington.EDU> writes:
>On Thu, 19 Jan 2006, Kevin Podsiadlik wrote:
>> Are there some email programs out there that can't handle the
>> underscore character in a username properly?
>
>I'm not surprised. There are plenty of programs (especially f*cking web
>forms) which are under the misconception that "+" is not a valid character
>in an email address. Why shouldn't "_" enjoy the fun.
>

The "+" character is often used as the separator in the username on mail
servers which support subaddressing.

See for instance RFC 3598

The hyphen "-" is also often used in this manner.

The symptom reported of mail addressed to

xxx_y...@yahoo.com

being delivered to

x...@yahoo.com

would be consistent with yahoo.com treating "_" as a subaddressing separator.

David Webb
Security team leader
CCSS
Middlesex University