IP blacklisting is the one of the major crisis which we come across in Webhosting industry. IP’s appear on blacklist usually by sending unsolicited commercial or bulk email. There are a number of monitoring tools available. Each monitoring tool would give information accordingly. These monitoring tools generates alerts once there is spamming in your server. Manual monitoring is also a good key.
Possible reasons for blacklisting
- Sending out spam emails
- Sending out emails without authentication
- Using scripts to send out bulk emails.
- Adding spam trap address to your mailing list
Once your IP is blacklisted, whats next ?
First step is to determine whether your machine, or a machine sharing your IP address which is under your control is sending out spam. You can also use MXtool box to check your IP and on which all blacklist your IP is listed. If you are sure that nothing under your control is sending out spam, you can contact IP blacklist operators for removal of your IP from the list. If you don’t remove the cause for the spaming, delisting or attempt to move to new IP address may fail and may lead to more severe listing. Here are some links to removal of tools provided by a few of the most popular IP blacklist.
How is blacklisting done ?
Most of the blacklist authorities implement DNS- based blacklist. Once we check the IP, they would return with the blacklist details along with a link to contact to remove the blacklisting. One of the most famous blacklisting is spamhaus. Listing criteria for spamhaus varies greatly. Spamhaus maintains a total of 6 different blacklists, significant granular control can be achieved so that as little or as much spam can be classified as the end user desires.
Zones of blacklisting for Spamhaus
The XBL (Spamhaus Exploits Block list) is real time database ok know IP addresses of hijacked PC’s infected by 3rd party exploits. These can include, but are not limited to HTTP, SOCKS, AnalogX, Wingate, Formmail etc.
The PBL (Spamhaus Policy Block list ) is a list of IP address that have no reason to be delivering unauthenticated SMTP emails to any host on internet. The PBL is not maintained directly by Spamhaus.
The DBL ( SPamhaus Domain Block List ) is Spamhaus’s newest addition to their service. The DBL maintains a list of domains, usually websites URL’s that have been found within the body of the emails.
The ZEN blacklist is Spamhaus’s combination zone. You can either choose to make DNS queries to individual zones as listed above or combinations of them or use one zone, which includes them all. This is the primary zone that contains all of Spamhaus’s data and in turn is the zone that most people use.
The removal process of Spamhaus can very depending on the zone in which you are listed. Using a Blacklist Removal Center will show if you are listed, why and how to begin the removal.
How to use Blacklists ?
You can configure your mail server to lookup the senders IP on DNSBL, before accepting the mail from that IP. This can be done from control panel itself under the mail server configuration. Once enabled, for each email received by your server, it will check if the sender’s IP is listed on any of the blacklists. If it is listed, the email is bounced back to the sender along with the result received from the DNSBL.