[Mailman-Users] Some subscriber's e-mail adresses contains line break unicode character ​

[Stephen J. Turnbull]

Henrik Rasmussen writes:

 > In some occasions, a few subscribers of different lists contains
 > the character ​ in the mail-address, like
 > me at example.com​<mailto:me at example.com​>

This example doesn't make sense to me.  me at example.com can't be a real
address so you didn't cut and paste, and I don't understand why a
plain-text message would have HTML escapes in it.  (I guess maybe your
mail was pure HTML and autoconverted by mailman at mail.python.org?)  Do
these addresses really have an embedded "mailto:" URL?

Regarding the address itself.  I don't understand why an address would
have ZWSP stuck on the end.  I would expect something like
"First Last{ZWSP}<me at example.com>".

 > preventing them from receiving any mails from Mailman. The Unicode
 > is always the same on affected subscribers.

It appears that pasting from (some versions of? some plug-ins of?)
Google Chrome to other applications can have this effect.  Eg,

http://stackoverflow.com/questions/7055600/u200b-zero-width-space-characters-in-my-js-code-where-did-they-came-from

 > As what I've read it is a zero space line break unicode character.

Yes.  Technically, a zero-width space, which indicates a word boundary
and *may* be treated as a line-break point or a point for adding space
when text is fully justified.

 > What could course this and how can I prevent it?

Broken software (not Mailman) is injecting the character, and there's
nothing you can do to prevent it at present.  I expect that it's
occurring in the web interface, and my guess would be a list admin
copy-pasting into "mass add members" or a user copy-pasting a full
address with display name into the address field on the listinfo page.

To figure out what to do about it, it would help to have confirmation
that your me at example.com example accurately represents the
configuration that is occuring.

Mark may have a patch to filter these at subscription time and/or a
withlist script to remove them shortly.