Mail problems because of spam run after phishing

Some time ago, some Science users fell for a phishing mail, therefore their account could be misused by spammers to send mail through our mailservers. Therefore our mailservers ended up in blacklists yesterday evening. Some mails could therefore not be delivered to other servers, that mail was returned to the sender. This morning we removed the IP addresses of our servers from several blacklists, we think that the problems are resolved now.