SpamCop FAQ : SpamCop Mail Service : FAQ about Filtering and Held Mail :
If all your mail is being held, then your local mail server is probably listed in the SpamCop Blocklist (or another blocklist that you have selected). Often cheap ISPs, or forwarding services get used by spammers and then blocklisted.
Investigate a couple of individual mail messages by using the instructions in the FAQ Why did this message get held? and you should discover which server(s) are the problem.