I've had the same problem in the past. As a web designer I have many email accounts, at least one for every client account. One day my emails mysteriously started bouncing, even when I tested by setting a number of different "From:
me@domain1.com" email addresses in Outlook.
As it turns out, the problem wasn't with any of those email addresses in particular. My outgoing mail server is set to my local ISP, and it was the whole ISP that was being blocked by SpamCop! Apparently one or two naughty spammers can ruin it for everyone.
It takes time to get "delisted" from SpamCop. You might just have to be patient - and sign up for a Yahoo or Hotmail email address until the problem is resolved.
IMHO SpamCop is not worth the trouble they cause. They DID force my ISP to track down their rogue spammer, but at the price of inconveniencing thousands of innocent customers.