The block message is 521 DNSRBL: Blocked for abuse

Thu Sep 19 15:21:10 UTC 2013

On Wed, Sep 18, 2013 at 11:59:13AM -0500, John LeCoque wrote:
> I would say the first step is to find an immediate workaround for your end
> users - maybe bring up a VM on AWS or some other cloud provider to use as
> an SMTP relay while you work out the blacklist issue.

Not a good idea.  It's a best practice to refuse *all* email traffic
out of Amazon's cloud because (a) it's a prodigous source of spam and
other forms of abuse and (b) Amazon absolutely refuses to lift a finger
to address the problem.  (Just try submitting an abuse report and notice
all the hoop-jumping they've put in the way in a quite obvious, deliberate
attempt to make it as difficult as possible.)

---rsk