What sort of spam filter do you use?

  • Will I get any spam if I use your filter?
  • How do you know what email is spam, and what isn't?
  • Will you bounce emails you think are spam back to the original sender?
  • Some filters block legitimate email, what do you do to make sure that doesn't happen?

There are three spam filters in place.  The first bounces messages back to the sender if their IP address is on known spammer IPs.  The only way someone gets on that list is if they have sent at least a couple thousand spam/viruses to fairly large companies who report them.  If someone has a virus on their machine, and is sending out gobs of viruses, they will end up blacklisted until they fix the problem.  Our servers will bounce the messages, with a link to a URL that says they have been blacklisted, so at least they will know that their emails aren't being received.  This blacklist is quite conservative (we have rejected other blacklists due to listing people too quickly) and we haven't had any trouble with it in the five years we have used it.  You can't opt out of this filter, as it is installed server-wide.

The second is called "greylisting." It delays mail the first time you get a message from someone. Some spammers don't know how to delay, so they give up, where real email servers will always retry.  You can opt out of this one.  (One customer asked to opt out, and ten minutes after he opted out, he got so much spam that he asked for it to be turned back on.)  If the sender's email server is broken and doesn't know how to delay, they will get a bounce message with a link to a web page explaining why it is broken, and our email address if they have any questions.

The third method is called "spamassassin" and this does various checks on the content of the message, and scores them appropriately.  This filter will (by default) not block any messages, but "tag" them with a header, and then you can setup your mail client to automatically filter them into a spam folder.  Each customer decides what tag level is appropriate for his needs.

We believe that having messages thrown away due to spam filtering without letting the sender or the receiver know is wrong, and so our system will never do that. We also have a very low tolerance for spam, and so work hard to get the filters working well.  If you do get a spam email that slips through, you can submit it to spam@limedaley.com to train our filters so that they will be more likely to be able to catch that sort of spam in the future.

So, yes, you will get some spam, but we believe this combination of spam blocking and tagging to be the best automated spam filtering that one can do.