Realtime Black List (RBLs) uses the DNS protocol to query the well-known IP addresses which have been complaint to send worm, virus & junk mail. Using RBLs to prevent junk, virus & worm email is very effective. The algorithm of RBLs is different with that of Anti-Spam and Anti-Virus services as RBLs works based on IP address, while Anti-Spam and Anti-Virus services work based on the message content.
EmailArchitect server has several built-in rbls servers by default. You can find more rbls servers by the following url: http://rbls.org.
In EmailArchitect RBLs Service, the white email addresses list and IP addresses list are available to prevent the RBLs from blocking normal message incorrectly.
RBLs is not 100% correct! "Trusted SPF/MX/A records" option can be used to prevent the RBLs from blocking normal message.
Please learn more detail about Sender Policy Framework(SPF) from the following url:
Although SPF is a good solution to prevent faked email sender, many domains have
not yet set the SPF record to support this function. As such, checking the MX/A
record is very important for these domains.
The email sender is: email@example.com and this email is from IP address: 18.104.22.168. By querying the dns server of adminsystem.com, mail.adminsystem.com is the MX record of adminsystem.com and the IP address of "mail.adminsystem.com" is "22.214.171.124". There is enough information to validate this email. The RBLs will never block this IP address even this IP address is list on the rbls servers.
Now, more and more rbls servers list the dynamic IP addresses to prevent bulk mailer to spread junk mail. To let the local user to send email from dynamic IP addresses, the user must set the user authentication in email client. If the user set the user authentication, the RBLs will never block the connection.