As someone who learned HTML and CSS in the 2000s, it's really hard for me to give up my CSS and code in tables. But the more I design and create email templates, the more I realize that I need to get over this complex. Here are some more best practices that I've learned about designing, coding, and sending emails.
Keep It Simple
I've designed really complex email templates before, usually at the request of a client. While they always end up looking pretty good, I can never get them to look perfect in all email clients, and it takes a long time to do all that testing and make sure everything looks good. All of those images, fonts, and colors look totally different in Gmail than they do in Lotus and totally different in Yahoo than Apple Mail for iPad. And really, within each of those email programs, there are a ton of settings that will change the way an email looks. Some people block images and some people block all HTML markup.