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

Mark Sapiro mark at msapiro.net
Wed Oct 21 05:59:02 CEST 2015

On 10/20/2015 01:52 AM, Henrik Rasmussen wrote:
> 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​> preventing them from receiving any mails from Mailman. The Unicode is always the same on affected subscribers.

I am confused. Are you saying the addresses end with an actual Unicode
zero width space character or that they end with the ascii string
'​'. If the latter, I don't see how this can happen. In no version
of Mailman 2.1 back to pre 2.1.1 has a ';' been allowed in an email
address. If the former, an address with '\u200B' (the python escape for
that character) in the domain would not have been allowed since Mailman
2.1.15, but may have been allowed before that.

> As what I've read it is a zero space line break unicode character. So far the only think I found was about HTML pages containing the character and a single post explains something about the character being added to a page through the Office 365 Public Website editor. But since subscribing to a Mailman list does not involve an editor, I assume that the character could have been added by a webbased mail client.

That is probably correct, but gmail's web mail in particular (which I
once thought was good about stuff like this) and probably others when
composing in 'rich text' and creating a multipart/alternative message,
sometimes creates a text/plain alternative littered with these characters.

Thus, if one composes an email in Gmail's web client to the list-request
address with a body line

subscribe me at example.com

It is possible the text/plain alternative will have a zero width space
appended to the address.

> I don't know whether the subscribers have subscribed through mail or through the Mailman web interface, but since the problem is random, I assume that the Mailman web interface is not associated. I guess that it must be some kind of common web based MUA they have used, like Gmail or Hotmail or similar.

Have you looked at Mailman's subscribe log?

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

Conjecture on cause above. Prevention - upgrade Mailman to >= 2.1.15

Mark Sapiro <mark at msapiro.net>        The highway is for gamblers,
San Francisco Bay Area, California    better use your sense - B. Dylan

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