Same just happened with abuseat, without spamhaus, when modifying my email address on OVH, I couldn’t receive a confirmation code because OVH mail was silently rejected as a spam.
postfix/smtpd[3229311]: NOQUEUE: reject: RCPT from mo401.mail-out.ovh.net[51.254.194.161]: 554 5.7.1 Service unavailable; Client host [51.254.194.161] blocked using cbl.abuseat.org; from=<ch9367-ovh@undelivered.ovh.com> to=<mail@domain.tld> proto=ESMTP helo=<mo401.mail-out.ovh.net>
That’s really an issue to consider, I’ve totally removed any spam filter from my postfix config, rather have spams in my spam box than having important emails silently rejected without any information !