I'm still getting this warning too, and half of the mailing list goes
into my spam folder.  This seems to be the problem:

Received-SPF: none (google.com: owner-vanagon@gerry.vanagon.com does
not designate permitted sender hosts) client-ip=71.126.148.6;
Authentication-Results: mx.google.com;
       spf=neutral (google.com: owner-vanagon@gerry.vanagon.com does
not designate permitted sender hosts)
smtp.mail=owner-vanagon@gerry.vanagon.com;
       dkim=neutral (body hash did not verify) header.i=@gmail.com;
       dmarc=fail (p=NONE dis=NONE) header.from=gmail.com

Looks like the SPF record for vanagon.com is malformed (too many quotes)

should be:
vanagon.com.        1800    IN    TXT    "v=spf1 include:_spf.google.com ~all"

DKIM is not being resigned after the listserv processing and there's
no DMARC.  But I guess fixing the SPF record would make gmail happy.

Ryan

On Sat, Apr 26, 2014 at 7:44 PM, Don Hanson <dhanson928@gmail.com> wrote:
>   Has anybody else recently began getting these Gmail  "!Warning! May not
> have been sent by ____________......" message headers with a lot of vanagon
> list  emails?   They began appearing a few days ago,  on top of lots of the
> posts from Vanagon List that I've been getting.  Gmail has a convoluted
> explanation in a drop down menu that I don't follow, being a
> cyber-challenged...I  don't think I have changed anything in my settings to
> cause these highlighted headers to began appearing...but ....?
>
>   Don Hanson