As more of your competitors begin to use email marketing aggressively, the pressure is growing to make your messages stand out. In addition, because your target audiences are over-messaged, you only have an average of three seconds to capture their attention and get them to take your desired action. That's why you need to consider every aspect of your email's creative strategy and execution. Here are some tips to help you improve the effectiveness of your email messages:

Keep it relevant. Readers of email are merciless. If your messages are not targeted to their needs, they will quickly delete your message or, worse yet, they may unsubscribe from your mailing list. To increase the relevance of your messages, think about how to make creative connections with what's going on in your readers' world. Possibilities include holiday and seasonal promotions, connections to major news stories and entertainment events.

Optimize text for scannability. Remember, most visitors won't read your entire email but will simply scan it, looking for clues to quickly answer their questions. For best results, use short blocks of text and bullets to make your message easier to scan. A call to action should be visible "above the fold" - that is, within the first screenful of information that the reader will see. Make sure that any links are clearly formatted as clickable links. If you're using images for links, make sure they look clickable as well (for example, a button that contains the words "more information" or "order now").

HTML considerations. Different email programs render HTML differently. They may display table, style and background formatting and other HTML elements in slightly different ways. So it's critically important to test your messages in all of the major email clients, including Microsoft Outlook, Eudora, Hotmail, Yahoo! Mail and Google Mail.

Use images sparingly. Given the size of the email canvas, it's tempting to want to fill it with large, complex images. But don't do it. Larger images take more time to download than smaller ones. Also, because of security concerns, some email programs are set up with images disabled. Your message should be understandable, even if the images aren't visible. Try viewing your test message in each email client with the images turned off, so you can identify problems and make any necessary design changes before you send your message to your readers. For best results, use a balance of words and images in your messages.

Rich media. Embedding Flash, video and audio into emails is a powerful way to add impact to your campaigns. Depending upon the level of sophistication of your target audience, however, they may not be able to view Flash movies or respond to them. Proceed carefully with rich media.

The relationship between testing and creative. One of the best ways to refine your email creative strategy is through testing. Split your email list and send each segment a variation of your message's text, images, layout and other elements. Then analyze the resulting data to determine your readers' preferences, and optimize your future messages accordingly.