As web designers, we’ve grown pretty good at understanding how to create a modern, semantic, accessible website using XHTML and CSS. We understand what makes a good website, and how to make it happen.

When it comes time to design emails though, do all the same rules apply? Are there things we should be doing specifically for email that don’t make sense on a website? Campaign Monitor has published an article of 2008 Email Design Guidelines that shows us the technical, design and information elements that make up a successful HTML email.

• Don’t waste your readers’ time — An email inbox is a busy place, you won’t get much attention.
• Permission matters — Not only do you need to have permission to email people, but it helps to remind them of how they gave you permission, as specifically as you can.
• Relevance trumps permission — Just having permission is not enough, the content you are sending must also be relevant.
• Make unsubscribing easy — There’s no point emailing people who are not interested.
• Image blocking is common — You can’t rely on people actually seeing your images.
• Bring back tables — Structural tables are still often necessary for creating columns.
• Add inline styles — Gmail removes anything else.
• Don’t forget your plain text version — You can make blocks of text more readable.
• Meet your legal obligations — For example, CAN-SPAM for US senders.
• Test, test, test — It’s the only way to be confident about your design working.

Source: 2008 Email Design Guidelines