February 1 2021

Failure to deliver emails due to an expired Spamcop domain.

One of the most popular spam block lists seems to have forgotten to renew the domain. In the meantime, all IPs have been blocked.

Spamcop spam block list operators were unable to renew their domain. This temporarily led to numerous undelivered emails. The website has meanwhile led to a standard domain registrar page, on which advertising is displayed. Spamcop has been part of Cisco for several years.

Spamcop maintains a spam block list, which email hosts can check to see if the IP addresses are known to spammers. There are a few of these blacklists, Spamcop being one of the most popular. These are requested via DNS (DNSBL)

SpamCop responded as if all IPs were spammers.

With such blacklists, an IP is written backwards and then the host name is added to the blacklist. If it returns an empty DNS response, it means that the IP was not noticed as a spam sender. If, however, a response is returned, the IP is listed.

Spam blacklists can be used in several ways; some mail hosts block emails directly if the sender's servers are in one or more of these lists. You can also use a list in that blacklist as one of several spam rating criteria.

The standard domain host page is currently configured such that DNS returns an IP for all subdomains. In effect, this means that every request for any IP leads to a response which the mail server interprets as a list. In other words: for Spamcop, everyone is a spammer.

Spamcop is managed by Cisco

Spamcop is currently part of Cisco. The service was originally founded by an individual in the 90s and later bought by the Ironport company. 

Ironport, in turn, was taken over by Cisco in 2007.

In our tests, the Spamcop website is now partially displayed again and the correct results for DNS queries are returned again from some DNS servers. Apparently the domain has been reactivated in the meantime, but it will take a while for all DNS servers to adopt these changes. It is likely that the incident caused some emails to fail to deliver, as many mail hosts use Spamcop.



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