If there is one thing every internet user agrees on, it has to be this: SPAM sucks. We have come a long way in the past few years – we now have sophisticated spam blocking software, authentication technologies like SPF, even hardware spam filters like the Mail Foundry we use here at SingleHop to provide spam filtering services for our client’s mail servers.
One method of keeping SPAM under control on the internet is to keep track of SPAM recieved and then prohibit the author of the SPAM to send further mail to your system. This method, called a blacklist, sounds simple in theory but has a number of non-trivial implementations in practice. Blacklisting an address might work for a short time, but addresses are easy to come by, and domains only slightly more difficult to obtain. The next step would be to blacklist the IP address the SPAM originated from. Since there is a limited number of IP addresses, and their allocation is managed rather tightly, banning an address from ever sending mail to your system is actually a pretty good way to keep up your signal-to-noise ratio.
If you decided to keep your own blacklist of addresses, it might take you awhile to get wise to the spammer hosts online. Luckily, there are existing systems to publish lists of offending addresses and make it easy for mail software to reject mail from those addresses. For instance, the DNSBL system, invented by Paul Vixie (of vixie-cron fame) as part of his MAPS system, allows mail servers to look up offending addresses using the DNS system. If you are a large email provider like Hotmail and Outblaze, you could quickly build your own lists of spammers, and in fact these providers maintain their own internal blacklists.
All of this infrastructure sounds great for end users trying to keep their inbox clear. But it is a huge bother for service providers like us. Like most hosting companies and dedicated server providers, our terms of service and spam policy prohibit sending spam. But occasionally, clients use their machines to send unsolicited mail anyway, or host their ‘spamvertised’ websites with us. Occasionally, also, client’s machines are hacked and used to send SPAM. As a result of the SPAM originating from our network, portions of our IP Address space are sometimes placed on blacklists. If we are lucky, only the addresses used to send spam are blacklisted. Often, the entire customer subnet is blocked. In particularly egregious instances, entire class C subnets have been blacklisted!
This is a potential problem for you, our clients. When you buy IP addresses from us, you don’t want to find out that huge segments of the internet won’t accept mail from you! And we don’t want that either – our job is to make your server with us can do all the tasks you require of it.
As a result, we have spent, and continue to spend, a lot of man-hours dealing with blacklistings of our IP space. We are in constant communication with well-known DNSBL providers like Spamhaus and email providers like Outblaze, removing blacklistings, improving our policies and keeping our networks clean. Recently, however, I have created software tools which make the job more manageable for us and more reliable for you. Here are some of the things we now do to ensure you can send your email:
* Automated tools now check every subnet before it is assigned to a client to make sure it’s not blacklisted.
* Spam complaints from services like Spamcop are automatically processed and forwarded to your account executive, ensuring we know about spam problems instantly and can deal with them right away.
* Many mail servers require that reverse DNS information be correct before they accept mail from you – we set this information automatically!
* Without valid whois information, individual customer subnets cannot be identified and so entire Class C networks are sometimes blacklisted. We set your whois information automatically, so you will never be affected by other problems on your Class C subnet
These new tools have enabled us to be proactive in keeping our networks clean. Other providers wait until you’ve complained to them about mail delivery problems to take action. We have already cleaned up your subnet before you even began using it! So go ahead, run your own mail server with us. We promise, we’ve made it easy for you.