Most email clients support HTML, however not all do. It's possible that some people may not be able to read your messages if they are using an email client that supports only TEXT messages.

Disadvantage of sending text email: You will not be able to accurately track your messages in our system if you send them in TEXT format - such as the number of people who have opened your message, etc.

However if you get better results when you send your ads in text mode, you can always track your own messages rather than 100% depending on our system for tracking. Ultimately, your choice should depend more on better response/sales rather that what our tracking stats say.

So which one is better? - the choice is yours. Since you have both options, you can split test your ads and find out which gives you better response.

Let us know what you think!