Spam control is a necessity if you use e-mail which the vast majority of us do. And although PCMech has covered spam control with several articles on the subject, the methods change from year to year - so consider this an update for the 2008-2009 era of e-mail.
Client Side
With e-mail clients you have free and paid options but I concentrate on the freebies because I don’t consider spam protection worth the cost unless it’s in a corporate environment with hundreds and/or thousands of users.
The best freebie spam protection I’ve used client-side is the adaptive junk mail filter in Mozilla Thunderbird. Adaptive translates to "learns as it goes". When you first enable the filter Thunderbird will still deliver spam to the inbox until you flag it. The more you flag, the more the filter "learns" what is spam and what isn’t and filters appropriately over time. When used in concert with its built in address book (for whitelisting - more on that in a moment) it does the job well.
For those that would ask "How long does the ‘learning’ process take?", it’s all dependent on how much spam you get. The more you get, the longer the process takes. But even if you receive a ton of spam to the tune of 200 per day (which is extreme), the adaptive filter will be able to learn most of that in a few weeks.
Server Side (Domains)
If you have your own domain and pay for web hosting, you most likely use domain-based e-mail, such as you@your.domain. There are server-side options you can set in your web host’s control panel to slow the spam down.
SpamAssassin
Most web hosts (even the cheap ones) have SpamAssassin - which is an awesome spam filter. Lots of options, lots of control. Under most circumstances you should be able to instruct SA to modify the subject line or e-mails it thinks are spam. For example, if a spam is received and the subject line is "hello", SA will change it to "*****SPAM***** hello" before delivery to your inbox so it’s really easy to spot upon receive.
In addition, if you use the Mozilla Thunderbird e-mail client it has options to "trust" SpamAssassin based on e-mail headers.
SPF
Sender Policy Framework is an absolute necessity when using domain-based e-mail. This is not a filter per sé but rather a "challenge response" to stop spoofed e-mails.
If you run into the situation where all of a sudden you see tons of "Message could not be delivered" for mails you never sent, all with spam-ish looking subject lines, your domain mail is being spoofed. SPF will take care of this 99% of the time. Once enabled it takes a few weeks and then the spoofs will stop.
Whitelisting / Blacklisting
You can whitelists (addresses you want to receive mail from) and blacklists (addresses you want to block) on a server side level but there is some debate as to how effective it is compared to having a client do it.
If you’re the kind that uses a web-based version of your domain-based e-mail, utilizing server side lists of this type would serve to your advantage. If using a client, let the client do it.
Web-Based Free E-Mail
Example of freebie web-based mail services are Hotmail, Yahoo! Mail, AIM mail, Gmail and so on.
Freebie web-based e-mail compared to clients and/or server side differs because your options are much fewer as to what you can do. However there are things you can do now to take control of the spam.
Always use your Contact List / Address Book
With most freebie web-based mail, anyone listed in your Contact List is automatically whitelisted. So for friends, family, biz contacts and other types of mail you want, use that list and use it often.
It is better to have direct delivery instead of forwarded mail
Mail which is forwarded to you from another e-mail account runs the risk of bypassing the spam filters (even on Gmail) because it is in fact a forwarded mail addressed to you.
You’re better off not having anything forwarded, trust the spam filters provided by the freebie service and let the filters do their job. The more mail you have forwarded in, the more likely you are to have spam directly in your inbox - no matter how many times you flag it otherwise.
Stay inside the web interface
Spam filters work better on freebie web-based mail when using it in its intended environment - the web browser.
Example using Gmail:
Instead of using the Gmail interface you decide to access the mail using a mail client instead such as Mozilla Thunderbird. When spam comes in you flag the spam in Thunderbird, but it’s not using the Gmail reporting method but rather the internal client method. Gmail is never notified of the spam you reported so it will continue to arrive in your inbox. If you stay within the Gmail interface and flag spam there, Gmail "learns" what is spam and what isn’t - which is what you want to stop it from appearing.
For other e-mail services where you download mail via POP, the same applies. Flagging spam in a client never notifies the e-mail service you flagged it, decreasing spam prevention.
Not using your true e-mail address
The reason web sites like BugMeNot exist is because people get sick and tired of signing up for stuff only to find it nearly impossible to "de-sign" your e-mail address later.
You do have a few options here, all of which work well.
Using an alternative "don’t bug me" e-mail provider
The best example of this is Mailinator. You can fabricate e-mail addresses out of thin air in seconds. However there’s one serious drawback - you always have to go to that site to get the mail delivered there (very inconvenient).
Linked accounts
This is by far the absolute best way to have a "throw away" e-mail address you can easily access while still using your primary account.
The service that does this best is Hotmail because it’s stupidly easy.
If you use an @live.com, @msn.com or @hotmail.com account, login to it, then go to Options and click "View and edit your personal information" under "Manage your account". On the next screen there are options for "Linked Windows Live IDs". From here you can link other Hotmail, Live and/or MSN accounts to your primary account. If you want to add one, go ahead. If you want to add more than that (I have 5), go ahead.
When you’re done, in your normal Hotmail interface at the far right you will see your e-mail address. This can be clicked and you can switch over to your other account instantly.
The beauty of this setup is that your e-mail addresses stay separate. They are linked but do not share inboxes. So whenever you want to check the other account, all it takes is two clicks.
This is free to do, by the way.
To note: AIM mail and Yahoo! also have linked account options.
Gmail does have the ability to poll mail from other accounts but has no linking ability (as in link 2 Gmail accounts together in concert).
What did I miss?
Do you have any spam prevention tips I missed? If so, please feel free to tell everybody in the comments. Any spam prevention is good spam prevention.