E-mail marketing is like the holy grail of advertising. It’s not only the best way to target potential customers (especially if they’ve opted in to your mailings), but it also lets you track how they react to your offers so you can better hone your message. And the best part is that it’s absolutely free.

But you can’t hone your message until you have a good tracking system in place. Typical metrics for e-mail marketing include:

* Sent: This is fairly obvious – it’s just the actual number of e-mails you send.

* Bounces: These are undeliverable e-mails. These occur for a variety of reasons, such as technical problems, bad lists, etc., but they can also be due to spam filters, which are software programs that ISPs and even consumers use to block unwanted mail. You should shoot for a bounce rate of no more than 10%.

* Delivered: This is the number of successfully sent e-mails (minus the bounces). A good percentage to go for here is 80%, although less may be acceptable if your list is noticeably spam-filter happy.

* Opened: This is the number of e-mails that actually got opened on arrival. Good offers with strong content should garner rates of between 10% and 50% here.

* Unsubs: This is one to watch carefully. It’s the number of subscriptions cancelled after the mailing, and should never reach more than 5%. If it does, you need to significantly rethink your list or your approach.

* Clicks: This is the number of links within the message that were clicked on by the recipient. This is another area where you should be receiving at least 10% in responses, and if you’re not, you should be going back to the content drawing board.

* Landing page activity: The landing page is where recipients of your e-mailed offers land when they click on a link in the e-mail. Here, sites usually track exactly what the visitor did, including the number of visits, page views and quick abandonments. Success here varies depending on the offer and the site. Sometimes even the best e-mail messages perform poorly solely because of the quality of the landing page. One easy fix: Make sure the e-mail offer matches that found on the landing page. If it doesn’t, you’ve lost a potential sale.

* Actions: This is the gravy – the amount of orders, leads, newsletter signups and so on that result from the mailing. This can range anywhere from 1% to 20%, depending on the offer.

All good marketing programs track these metrics at various stages and levels. It’s one sure way to ensure you’ve targeted the right customers with the right message.