Edited sentence: An email service provider thinking to add any blacklist should inform their userbase before the blocking goes into effect to allow their users to whitelist their contacts (i.As telephone companies continue to convert their static IP address blocks to the less expensive (for them) dynamic PPPoE addressing, businesses with previously static IP addresses are increasingly being flagged as "dynamic" by SORBS.Attempts to resolve this issue on the telco side without having the telco set the IP addresses as "static" has been reported as a near impossible task, although why is a mystery as SORBS clearly indicates the word of the regional Internet registry (ARIN, RIPE, etc) Points of Contact for a network will be taken as gospel concerning that ISP's networks.Providers who do not take this step risk preventing legitimate email from reaching their customers.Several businesses use low cost dynamic IP-based DSL accounts which do not offer a full service (e.customisable rDNS or static IP address).from their address book)