Recently my ISP enforced us to change the whole networks external IPs. I did that on thursday. Obviously has to change the external exchange IP address too. Since last night one of the domain user is having issue as under, I wanted to send an email to the same domain as well but the same issue as under. I can send emails to lots of domains. Never had this issue before. Where do I seek help? is microsoft doing something or my ISP?
One of my domain user is trying to send an email to a specific domain and the message bounces back as:
<mail.mydomain.com #5.7.1 smtp;550 5.7.1 Service unavailable; Client host [72.xx.xxx.xxx] blocked using Blocklist 2, mail from IP banned; To request removal from this list please forward this message to firstname.lastname@example.org.>