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I've been blacklisted but why?

My emails are being blocked by the receiving server, why?

What are email block lists?

Most Internet Service Providers (ISPs) and web servers use a collaborative service to help block and prevent spammers from doing their business.  These block lists (as known as black lists) are DNS based anti-spam databases.

Your IP Address might have changed, resulted in you being blocked. Or it maybe that you IP address has been flagged for some reason and blocked by one or many of the DNSBL (Domain Name System Black List) services, but why?

Assuming you are not a spammer of course, the most common cause is your PC (or a PC in your network) has been infected with either a virus or malware.  The infected computer has then been sending spam (junk unsolicited emails) on behalf of the spammer.

Another reason your IP could be blacklisted is through servers or routers being misconfigured to allow unauthorised users to send email through your ISP. These security holes allow what is called an Open Relay, and the spammers constantly search the Internet for vulnerable systems to use.

What is a DNSBL?

Domain Name System Blacklists, also known as DNSBL's, DNS Blacklists or DNS Block Lists are spam-blocking lists that allow a website administrator and ISPs (Internet Service Providers) to block messages from specific systems that have a history of sending spam.

If the maintainer of a DNS Blacklist has in the past received spam of any kind from a specific IP address, that server would be "blacklisted" and all messages sent from it would be either flagged or rejected from all sites that use that specific blacklist.

History of DNSBL.

The first DNSBL was created in 1997 and was called the RBL (Realtime Block List). Its purpose was to block spam email and to educate Internet service providers (ISPs) and other websites about spam and its related problems.  Almost all of today's email servers support at least one DNSBL in order to reduce the amount of junk mail clients using their service receive.

Since 1997 many other DNSBL providers have started up and they all have their own lists and methods of determining what is spam.  Some are stricter than others. Some sites only list the IP Address of a short time, on others it’s a permanent listing until you manually ask for removal (some sites charge for this).  Some DNSBL even block entire address ranges so you could be blocked on a DNSBL simply because of someone else’s spamming activity and also because the ISP hasn’t taken then necessary security measures to combat spamming from their networks.

The results are that some lists work better than others because they are maintained by services with a greater level of trustworthiness and credibility than competing lists might have.

What is SORBS?

Spam and Open Relay Blocking System, also known as SORBS is a service provided by Proofpoint Inc. (prior to acquisition in July 2011 was GFI software)  SORBS is another DNSBL service provider which effectively blocks emails from more than 12 million host servers known to disseminate spam, phishing attacks and other forms of malicious email.

History of SORBS

The Spam and Open Relay Blocking System (SORBS) was originally conceived in 2001 as an anti-spam project where a servers would check in real-time all received email to determine if that email was sent via various types of proxy and open-relay servers. 

How can I prevent being blocked?

It goes without saying that you should always ensure your computer is fully service-packed and running a good anti-virus solution, along with a good firewall to protect your private network.

The other option is to send your email via a trusted and secure smart host (such as outMail).  Prolateral contributes to the DNSBLs when profilter (our hosted anti-spam filter) detects spam and malware for its users.  Profilter protects the users from incoming junk email, whereas outMail is an SMTP Mail Relay.  Prolateral works very hard to ensure the outMail servers are blacklist free, and its sender reputation is the highest possible.

In addition Prolateral supports and works with feedback loop (FBL) systems run by large ISPs (Such HotMail, AOL, GoogleMail, etc)

About Prolateral

Prolateral Consulting is in business to put your organisation back in control of your own Information Technology, specialising in information and messaging security, computer forensic services, and disaster recovery planning.

Contact Info

Prolateral Consulting Ltd
Luton, Bedfordshire, UK
Tel : +44 (0) 8450 763760
Email : This e-mail address is being protected from spambots. You need JavaScript enabled to view it

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