TemasekTech does not control the Email Blacklists we are using. Spamhaus and ORDB Open Relay Database are highly respected Email Blacklists that do not list an ISP's IP indiscriminately. Your ISP's IP are blacklisted only if they are proven to spam or are being used by viruses or trojans to spam or send out viruses.
If your ISP is blocked, we strongly suggest that you bring this up to your ISP. If they are indeed block by these lists, they have much more to worry than just emails being blocked. Some of their users' accounts may be compromised or they are hosting some spammer criminal gangs.