One of our servers is currently listed by Spamcop. Due to this listing you may find that some emails were returned to you citing the Spamcop listing. Emails will only be returned by systems utilizing Spamcop as a blacklist, which Spamcop itself warns against doing, as it will likely block many legitimate emails.
We have changed our server to send messages through a different IP so no further emails will be blocked. We apologise for any inconvenience caused by the listing. Although it is impossible for a Spamcop listing to correctly reflect an active spammer using FastMail.FM (because our automated systems immediately lock out spammers), problems with the Spamcop listing algorithm nonetheless cause FastMail.FM to be listed from time to time.
If you were impacted by these problems in Spamcop's algorithms, please consider contacting the person you were sending to through some other means, and ask them to send the following to their ISP:
Dear email administrator,
I recently had an important email blocked from reaching me. This email was blocked because you use the "Spamcop Blocklist". The email came from a server that does not have any active spammers.
Spamcop say about their blocklist (at http://spamcop.net/bl) :