Preventing image suppression in HTML emails

According to MarketingSherpa’s 2010 Email Marketing Benchmark Report, only 33% of email users say they have images turned on by default in their email clients.
This means that if you do not consider optimizing email when images are turned off,  a large majority of your subscribers will not see your message properly and, as a consequence, they may simply refuse to read it or even to open it.
Obviously, it is not possible to prevent image suppression in every email client but you can still improve how your emails render even with images blocked by using a simple and inexpensive work-around: the alt-text tag.
Adding alt text is really simple, simply specify alt=”your text” inside the <img alt=”” /> tag:
e.g. <img src=”special_offer.gif” alt=”Buy now! Save $100″ />

Be Relevant – Make sure to add only well-written and relevant ALT Tags so that your readers can easily “preview” the actual email content before images are loaded.
Always use them – Remember to add them on all images (logo, banners, phographs) included in your html email. Obviously, it is not necessary to use them on purely decorative images (for ex. bullets).
Use captions with ALT tags – Some email applications, e.g Windows Live Hotmail and Yahoo! Mail, will not even display the ALT tags in the preview pane. Consider using captions (in HTML text) in addition to ALT tags.
Design with images off – To avoid these issues related to blocked images design your message with images off, so you know exactly if email content makes sense even without images.