Sometimes IP addresses can become blocked if they have been reported as spam on a DNS (Domain Name System) based anti-spam database.
If an IP address is blocked this can affect your VoIP service.
IP addresses can be blocked if at one point your IP address was flagged for some reason and blocked by some servers. (It could be that someone who was once assigned that IP address was blacklisted.)
How do I get an IP address removed from a blacklist?
If your IP address has been blacklisted and you want to investigate, then you will need to visit the blacklist's website and do a lookup on your IP address. Most blacklist databases will provide general listing reasons, but do not list specific email addresses tied to blacklisted IP addresses.
If you are able to find out why you were blacklisted, you can try to get it reversed - please contact our Support Helpdesk so that we can assist you.