<snip long list of spammy domains>
Just as another data point, the domain names you listed hit on enough URL
blacklists that Spamassassin quarantined the message for me (and would
have rejected it during the SMTP transaction had the NANOG server not been
listed on DNSWL-High). Spam hosts plus fake ASN = paging the Spamhaus DROP
maintainers to the white courtesy phone....
I do believe, as has been pointed out to me elsewhere that this is what
shows up when there's a 64 bit ASN and router software that doesn't grok 64
bit ASNs
So, completely by chance that one such as belongs to what looks like a bulk
mailer
--srs (htc one x)
I strongly recommend that you read about and fully understand how 4-byte ASNs work, and their use of AS23456 before you continue this thread.