DNSBLs (DNS-based Blackhole List, a.k.a RBL: Real-time Blackhole List) are lists of IP addresses published through Domain Name Servers which are mostly used to publish the IP addresses of computers or networks found to be spamming. Mail servers can be configured to reject emails sent from the IP addresses listed in these "blacklists".
Besides having your emails deferred from recipient email servers unwanted spamming will use precious network resources. Possibly leading to:
Below are some sites that have more information about DNSBLs.
It is a good idea to monitor the IPs of:
Different lists have different rules for the listing to occur. Possible reasons to get listed is listed below but may not be limited them.
Some possible causes to get listed is listed below but may not be limited them.
Reverse DNS (rDNS) lookup is finding the domain name (PTR record) that is associated with an IP address. You can find more information about rDNS lookups on Wikipedia.
Your rDNS is usually controlled by your ISP and can be changed by them. If you need to change it you should contact your ISP. Some ISP's can occasionally change your rDNS by mistake.
It may not make that much difference if you are just an ordinary user, but if you are providing services it may effect your users and services. Such that, email delivery rates may drop because some mailbox providers consider rDNS records when filtering email for SPAM and may reject email that are generated from IP's that do not match their reverse DNS records.
Reverse DNS is mostly used for:
BLalert comes into action here. It checks all 131 DNSBLs every single day for 365 days and reports the results back to you.
New! BLalert also monitors for changes in your rDNS. Keeping you aware of unwanted changes.
Checking 10 IP addresses against 131 DNSBLs every day for 365 days is a total of 478,150 checks!
If you try to manually check the 10 IP addresses against 131 DNSBLs every day, and lets say that every IP takes 30 seconds to check. It would take in total 30 hours to check them every day for 365 days.
We try to check all your monitored IPs at the same time. (Maximum 10 at a time.) So you will likely get all alerts in the same message.
We check your rDNS record everytime we check for blacklisting and tell you if there is a change.
You can choose to be alerted if the IP gets listed and/or when the IP gets unlisted. You may also choose to be alerted after every check as long as its listed.
Emails are standard. But you can also add GTalk contacts. You can be notified on your smart phone or through the desktop app?
Adding in the whole team or your customers contact is not a problem. You can also chose which contact gets which IP's alerts.
We will keep every result of our checks for the last 365 days and provide you with graphs on how your IP address is doing. New! We also keep a history on your rDNS.
You can download the data in a CSV format anytime you want.
Weekly, monthly or quarterly reports on how your IPs are doing. You decide which contact receives the reports.