Have you ever had an important email go missing? An important customer order that just doesn't arrive in your inbox? Well, the the first place to look is your spam filter. There's a good chance that the email may have gotten flagged as a "false positive" for spam. If you check your spam filter, you'll find the message. As long as you only need to look in one place, it's a quick detour.
The exact numbers vary, but according to a 2010 report from the Messaging Anti-Abuse Working Group (MAAWG)in the first half of 2010 covering about half a billion mailboxes, spam accounts for 88-92% of all mail.
With such a high volume of junk, its tough for your one important message of the day to get through properly.
We typically recommend filtering mail BEFORE it gets to your mail server. We've been working with Postini for years and find it to be an effective solution, but there are many other options. Filtering spam on your desktop means that spam will still show up on your smart phone and if you filter in multiple locations, it becomes difficult to track the "false positives". Some people may assume that two filters will help, but it just means more places to look for the false positives. Problems really pickup when users unknowinglyrun two spam filters. Perhaps your junk filter is on in Outlook, or you change a setting directly on your mailserver (often controllable by the user in webmail).
Bottom line - select ONE spam filtering solution that's effective and get rid of the spam BEFORE it even gets to your mail server. Unfortunately, the spammers aren't going away, so its just one more thing to deal with on your computer. No filter will be perfect, but if you can efficiently check for false positives in only one place, you'll make things much easier for yourself.