In order to help protect our network against spam, we implement various anti-spam mechanisms. One of these is the implementation of what is known as DNS RBL's (Real-time Black Lists), otherwise referred to in short as DNSBL's. These black lists are maintained by third parties and consist of a database of IP addresses, networks, domain names, or machines that are detected and reported as sending out significant amounts of spam e-mail across the Internet. The database is made up of the reports from other ISP's and mail providers around the world, and a large number of hosting providers or companies accepting inbound e-mail use these DNS BL's to reduce spam coming into their network.
When an inbound e-mail is received into our network, we may consult these various RBL's online to see if the sender or sender's network is listed and known as sending spam. If they are, we may reject the message and generate a bounce-back to the sender alerting them that their message was rejected because of this blacklist, and also provide a link for them to lookup and resolve the problem.
Here is a visual representation of the e-mail process with DNSBL's included:
Why do you reject the message rather than flagging it as ***SPAM***?
Scanning an e-mail to determine whether or not the contents may be spam related is very resource intensive, particularly when you consider our servers may be processing potentially hundreds of messages (or more) every minute. The more messages we have to scan, the more resources are consumed and the less power that is available to the server for serving websites and other features.
The DNS RBL check is performed at the connection level, ahead of any actual content scanning. This is different from traditional spam checking, which looks at the e-mail message and its contents to decide whether or not it may be spam. Instead, we look at the reputation of the sender and the sender's network to see if they are known as sending out a lot of spam before deciding whether or not to allow the e-mail to pass through. In short, this saves a lot of time and resources. Here is a visual representation of the entire e-mail process, including DNSBL checks and actual spam checking:
How accurate are the blacklists? Could my provider be listed in error?
We have carefully chosen specific blacklists that provide extremely accurate listings. While we certainly cannot say for sure that any listing is a mistake, the likelihood of this happening is extremely small.
Blacklist providers typically do not list a server or domain name for sending one or two spam messages, but hundreds to thousands (or more) - and within a short time-frame. The reliability of these reports is usually very good.
How do I fix the problem?
It's important to understand that the problem is not with your domain, e-mail or hosting account with us and that, instead, the problem lies with the senders network or mail servers and their poor reputation. To resolve this problem, the sender of the e-mail needs to contact their mail or network provider and provide them with a copy of the bounce-back message that our systems have sent them. This will tell their provider that they are blacklisted, and will also provide them with the necessary information for them to determine where they are blacklisted, and also how to resolve the issue.
Once the sender's network have resolved the problem and increased their reputation, the black list providers will remove them from the DNSBL's and the messages will then be accepted by our network.
But I'm not having this problem elsewhere, only with this*!
We're sorry for the inconvenience that this may cause. It should be noted that we are not the only company out there that are using DNSBL's to reduce spam on our network, and in fact a very large number of other hosting providers also utilise the very same lists that we do. There's a good chance that if a mail is being blocked by our network that it will also be blocked elsewhere. What we are doing here is not specifically unique to us. Different providers may use different blacklists, so behaviour will differ from provider to provider.
But all of my mail is being blocked!
That is not how this system works. It is important to understand that DNSBL checks are performed on each and every e-mail received to your account and only if the sender is listed that the message is rejected. This does not mean that every message sent to you is being rejected or blocked - only senders who are using servers that are known to be sending unsolicited or spam e-mail.
Can you just remove the blacklist or disable this system?
The blacklists that we use on our network are public blacklists, and we do not manage, maintain or even have access to remove any listings on these databases. As a result we cannot remove any entries from any blacklists.
In absolutely extreme cases where a large public mail provider have been incorrectly blacklisted, we may be able to provide a workaround or bypass - but this is extremely unlikely. If you have senders who are experiencing problems e-mailing you due to bounce-backs that are reporting blacklisting, they will need to contact the company they are sending mail through to resolve this.