[Mailman-Developers] What characters should be allowed in listnames

[Mark Sapiro]

I have just files <https://gitlab.com/mailman/mailman/issues/311> which
is about Mailman core allowing list's to be created with a slash '/' in
the name.

Core validates listnames by ensuring the fqdn_listname is a valid email
address. This is too liberal. RFC 5321 allows many characters in the
local part of a list name. We don't allow quite all of them, but we
allow this set [-0-9a-z!#$%&'*+./=?@_`{}~].

Since list names form parts of a URI, both in Postorius/HyperKitty and
in the Core's REST API, it is clear that characters that will cause
problems there should not be allowed. These include [#%&/?] and maybe
others. Additionally, I don't think we want @ in an email address local
part and + and = might cause problems with VERP which whittles it down
to [-0-9a-z!$'*._`{}~], but I'm thinking of being even more conservative
and going with just [-0-9a-z._].

I don't intend to change the email address validation except maybe to
remove @, but the code is such that an address with multiple @ won't
validate anyway.

I'd like feedback on this. What are your thoughts on what characters
should be allowed in list names?

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