See also https://www.reddit.com/r/sysadmin/comments/l9asw7/spamcop_domain_expiredparked/.

I noticed I'm not receiving e-mails recently. Checked the logs and found this:

mail_1                          | Jan 31 12:39:29 mail postfix/smtpd[21240]: NOQUEUE: reject: RCPT from $SERVER: 554 5.7.1 Service unavailable; Client host [$IP] blocked using bl.spamcop.net; from=<$SENDER> to=<$RECIPIENT> proto=ESMTP helo=<$SERVER>

Turns out the spamcop domain expired and now all lookups against the blocklist are treated as failures.

I assume spamcop will fix the domain issue. However, can the blocklist check be improved so that it doesn't reject all e-mail if the service is not available?