There’s a common bounce error from the Message Labs’ filtering appliance that goes no where.
501 Connection rejected by policy [7.7] please visit www.messagelabs.com/support
If you’re trying to troubleshoot a delivery problem and you find any reference to www.messagelabs.com/support, try http://www.symanteccloud.com/supportcentre/information/r_troublshooting instead. That link provides a little more information.
Return Path have an interesting post up about content filtering. I like the model of 3 different kinds of filters, in fact it’s one I’ve been using with clients for over 18 months. Spamfiltering isn’t really about one number or one filter result, it’s a complex interaction of lots of different heuristics designed to answer the question: do recipients want this kind of mail?
Read MoreA couple questions in the previous discussion thread about the Google privacy case. Both concern permission granted to Google to scan emails.
Google’s stance about this is fairly simple.
Gmail users give explicit permission for their mail to be scanned.
People who send mail to Gmail users give implicit permission for their mail to be scanned.
The plaintiff’s lawyers are alleging that some subset of gmail users – specifically those at Universities that use Google apps and ISP customers like CableOne – did not give explicit permission for their mail to be scanned by Google. They’re also arguing no senders give permission.
In addition to the lack of permission, the plaintiffs lawyers are arguing that Google’s behaviour is in violation of Google’s own policies.
Google thinks scanning is part of the ordinary course of business and they’re doing nothing wrong.
This is an interesting case. I think anyone who knows about email understands that the people who run the mail server have the ability to read anything that goes through. But a lot of us trust that most postmaster and admin types consider it unprofessional to look at mail without a decent reason. There are good reasons an admin might need to go into a mail spool.
Automated filtering is simply a part of life on the internet these days. Mails have to be scanned for viruses, spam and, yes, they are scanned for targeted advertising. I’m not convinced Google is outside the norm when they say that any emails sent through Google is personal information given too Google and therefore Google can use that information in accordance with their policies.
What makes the best email filter? There isn’t really a single answer to that question. Different people and different organizations have different tolerances for how false positives versus false negatives. For instance, we’re quite sensitive to false positives here, so we run extremely conservative filtering and don’t block very much at the MTA level. Other people I know are very sensitive to false negatives and run more aggressive filtering and block quite a bit of mail at the MTA level.
For the major ISPs, the people who plan, approve, design and monitor the filters usually want to maximize customer happiness. They want to deliver as much real mail as possible while blocking as much bad mail. Blocking real mail and letting through bad mail both result in unhappy customers and increase the ISP’s costs, either through customer churn or through support calls. And this is a process, filters are not static. ISPs roll out new filters all the time, sometimes they are an improvement and sometimes they’re not. When they’re not, they’re pulled out of production. This works both for positive filters like Return Path and negative filters like blocklists.
Then there is mail filtering that doesn’t have to do with spam. Business filters, for instance, often block non-business mail. Permission of the recipient often isn’t even a factor. Companies don’t often go out of their way to block personal mail, but if personal mail gets blocked (say the vacation plane ticket or the amazon receipt) they don’t often unblock it. But when you think about why a business provides email, it makes perfect sense. The business provides email to further its own business goals. Some personal usage is usually OK, but if someone notices and blocks personal email then it’s unlikely the business will unblock it, even if the employee opted in.
In the case of email filters, the free market does work. Different ISPs filter mail differently. Some people love Gmail’s filters. Other people think Hotmail has the best filtering. There are different standards for filtering, and that makes email stronger and more robust. Consumers have choices in their mail provider and spamfiltering.