Re: SPF records and DKIM signatures on ubuntu/postfix/mailman

On Fri, 2011-10-14 at 13:52 +1300, Robin Paulson wrote:
> i setup a public mailman discussion list recently, and the people who 
>  are subscribed via gmail are getting the following warning when they 
>  open messages sent via the list:
>  "This message may not have been sent by: <subscriber>@gmail.com  Learn 
>  more  Report phishing"
> 
>  the warning includes a link to this page, which gives a fairly 
>  comprehensive explanation:
>  https://mail.google.com/support/bin/answer.py?hl=en-GB&ctx=mail&answer=185812
> 
>  however, i'd like to get some further views on the matter.
>  is this a major enough problem to warrant doing anything about?
>  are users likely to unsubscribe when they see this message?
>  any suggestions on the best way to implement it, on a postfix/ubuntu 
>  lucid system?
>  anything else which is relevant?

 I had these sort of questions when I set-up my completely new mail host
and domain, and wondered if I would get spam-canned by the likes of
Google etc when I tried sending email.

 A lot of documentation suggests a minimum of rDNS entry (extremely
important for a new mail server), and SPF record. I did the rDNS, and
noticed a few places that grey-list new domains, but never had any
issues with lack of SPF.

 Having said that, SPF seems more prominent at this stage than DKIM, so
I would expect as situations change, SPF will become more mandatory as a
set-up item.

 I haven't had any reports of anyone seeing errors about my emails being
spam, but that's not to say some random block list won't get a report at
some stage.

 In this particular instance however, the error talks about relating to
email that appear to a user as originating from GMail, when they are
missing authentication records.

 So I would start by confirming your mailman set-up matches the sending
domain (not the sending user), so that GMail doesn't suddently
black-list your mailman set-up.

 Dagan


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