Most hosting companies these days offer some sort of spam filtering included as part of its hosting services. About 3 years ago we started putting new customers on our Barracuda SPAM Firewall. For the first few months we didn’t really know what it could handle and slowly put more and more domains on it. Not all domains were added but instead only one every few new hosting plans we received. Then, in the spring of 2008, our network was slammed with what seemed like an endless barrage of directory harvest attacks across multiple mail servers. The mass amount of email hitting our mail servers practically brought them to a screaching halt. The mail queues on our servers were backed up with upwards to 200,000 messages in the queue when they normally only have about 200 messages waiting. We quickly started adding more domains to the spam filter that we had been hosting for a while and found it to be very effective at taking the load off our main mail servers. Although the attack on our network wasn’t removed by adding domains to the spam filter it provided us the ability to keep email functioning correctly while our network engineers and security team dug deeper into the attack. Today, all new domains are automatically, without a second thought, added to our spam filter and as we come across older domains that aren’t being filtered for spam we add them as well.

When my ISP at home decided to add spam filtering for my home email address to say I was upset would be a slight understatement. I feel I’m very tech saavy and can handle my own spam filtering through the Outlook Junk Email folder, software add-ons and my own mental discretion. My biggest fear was that legitimate email was going to be filtered out and I was never going to know it. As time went by, I realized how much easier it was to download only the half dozen worthy emails instead of the 200+ junk messages every day that I had to sift through. I’ve come to enjoy having the spam filter doing all the work and don’t worry about the one lost email I might miss each year.

I don’t think some customers quite realize how much spam they receive on a daily basis until they get the filter turned off for a day. I had a customer the other day ask to have their spam filter removed. Some of their messages were being tagged as a low scoring spam message and they found it frustrating. They decided having no filter was better. I recommended they keep the filter but instead we make some adjustments to how it’s being filtered. They insisted it needed to be removed and so I conceded. Within 3 hours they were begging to have it turned back on.

Although I gave them numbers in advance, warning them of the amount of spam they actually receive they needed to see it for themselves. Although I don’t think they really receive that much email for one domain on a daily basis, it turned out to be more than they wanted to handle. Their domain received on average 800 messages per day. Most of this all went to one mailbox. Out of those 800 messages, 750 of them were being filtered out as spam at the filter level. Of those 50 non-filtered messages about 40 were low scoring spam and were being tagged. What the customer saw was 80% of the messages getting through as being tagged as spam and therefore the filter wasn’t nearly effective enough. In all reality, it was quite effective and in actuality, the settings were just right so that it never filtered out legitimate messages but instead let only a small percentage of real spam through. After we turned the filter back on, we made some minor adjustments to fit their needs and now everything is perfect for them.

For the people that enjoy numbers and statistics, here are some raw numbers from our spam filter for today as of 10PM EST.

Number of messages FlareHosting received: 625,082
Number of messages considered spam: 569,377
Number of messages containing a virus: 1,388
Number of messages tagged as low scoring spam: 1,372
Number of messages filtered out due to “rate limiting”: 1,038
Number of good messages: 51,907

Percentage of messages filtered out: 91.7%
Percentage of messages that were not spam: 8.3%

Imagine receiving 10 times as much email each day, most of which being spam. How much time would you want to spend filtering it all out yourself?