Q: I’ve read about e-mail “filters.” What’s a filter and how does it work?
A: E-mail filters are one way to screen your incoming e-mail. Some degree of filtering is built into virtually every e-mail program these days. Certain Internet Service Providers (ISPs) also filter e-mail at the server level to weed out some of the most egregious spam. Even if the ISP does not scan your mail for spam, you can do it yourself easily. You also can be sure your ISP hasn’t deleted any e-mails you actually wanted.
There are two approaches to filtering: blacklists and white lists. A blacklist tells the software, “I never want to receive e-mail from X.” A white list says, “I always want to receive e-mail from Y.”
For example, you probably always want to receive e-mail from your mom, but you probably never want to receive e-mail from some scummy spammer selling online porn. You also probably never want to receive e-mails with certain subject lines.
As an aside, although you wouldn’t think so, another thing that helps save time is to download only the e-mail headers. When 50% of the e-mail out there is spam or potential viruses, you do NOT want to waste your time downloading an entire e-mail you don’t want. When you download only headers, you see who the e-mail is from and the subject line, but not the entire e-mail. It does mean that it takes two passes to get your e-mail. But when you download headers first, you can ditch the bad e-mails before they get near your precious computer.
So, back to blacklisting and white listing tips. First here’s how to come up with a black list that works.
People often ask me what terms I actually use in my spam filter to kill spam, so I’m going to reveal a few tips that may help you kill as much spam as possible.
- No one you know EVER puts your name in the subject line. If one of my e-mails says “Susan” in the subject line, it’s toast. Putting your name on the subject line is an old marketing gimmick that has been overused.
- I only know a few people online who live in foreign countries. For example, I got 112 messages from the .jp domain. They are toast because I don’t know anyone in Japan.
- The big winner on subject lines is the word “prescription” with 479 bogus messages nuked automatically. No one I know would ever send me a message with that subject. And if they do, I don’t want to read it anyway.
Here’s a list of the top domains and subject line offenders and how many messages they’ve killed to date. (If you are offended by certain anatomical terms, skip down to White List Tips below.)
Top Level Domains
- .ru – 91
- .no – 38
- .za – 26
- .es – 69
- .se – 35
- .jp – 112
- .nl – 33
- .fi – 115
- .de – 308
- .cz – 33
- .dk – 50
Subject Line Text
- artmarket- 139
- penis- 130
- viagra – 265
- mortgage- 235
- sex- 95
- ADV – 27
- refinance – 71
- press release – 136
- lose weight – 36
- prescription – 479
- prozac – 36
- pharmacy – 85
- Susan – 777
- vicodin – 221
- RND_UC – 79
- daffron – 161
White List Tips
Of course, now spammers are putting every stupid misspelling possible into their e-mails, so it’s getting more difficult for blacklists to be effective. For example, I have a few alternate spellings of “viagra” with at signs (@) and so forth, but I won’t bother putting them all in because I have a white list as well.
My white list basically filters on my address book. If your e-mail address is in my address book, your e-mail is placed in a special folder called “White List.” So when I check my e-mail, I look at the White List folder first.
Then I go through the Received mail folder and do mass delete of the headers, which kills them off the server (recall I download headers first).
Certain e-mails are borderline, such as questions for Logical Tips. Here’s a few things I look at:
- A real subject line. Usually real people who are hoping for an answer from a real human are smart enough to put in intelligent subject lines. (Big Hint: if you habitually send e-mails with no subject lines at all, don’t expect a response!)
- A name that matches the e-mail address. If Joe White sends me an e-mail, I’m more likely to open it if the address is firstname.lastname@example.org, rather than email@example.com
- File size. I’m only downloading headers, but I can still see the file size in the list before I retrieve the full e-mail. If the e-mail is more than about 5K or 10K, I become suspicious of the e-mail and delete it. I only download attachments from people I know. Even then, if someone I know sends me a 900K picture, I may delete it because my connection is slow.
So that’s it. Clearly legislation isn’t going to do anything about the spam problem. But with blacklisting and white listing set up, I’m able to deal with the hundreds of messages I get every day.