Yahoo and "Filename contains lots of white space" rule

[Mark Sapiro]

On 1/19/21 1:58 PM, Ricky Boone wrote:
> Hello everyone,
> 
> I was seeing a disproportionate number of messages from legitimate
> @yahoo.com <http://yahoo.com> senders hitting our environment that, when
> they have an attachment with a long name with spaces, they hit the
> "Filename contains lots of white space" rule in filename.rules.conf. 
> Upon deeper inspection, it appears it may be something with Yahoo and
> how they handle spaces when generating the Content-Disposition header in
> the message.  In most cases, when the file name went past a certain
> number of characters, it was wrapped to the next line, but with 5-10
> blank characters padded to it.


See <https://www.rfc-editor.org/rfc/rfc5322.html#section-2.2.3>

Note that the filename= parameter in a Content-Disposition is a
structured field and should not be folded - try telling Yahoo that.

Are you saying that Yahoo is folding by inserting more than just a CRLF,
i.e. a CRLF and a TAB or multiple spaces. In that case, Yahoo is again
non-conformant.

However, none of that is helpful to you. There may be a MailScanner
issue if Yahoo is folding by inserting CRLF TAB and MailScanner is
considering the TAB to be multiple spaces. Is that the case?

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