The next thing that needs designing is the header, body, and footer. All three of them have the same features that can be changed the text style, text, and link. Much like the rest of the email, you should fit this style to your website, so if having a background matches your style, then give the email a background, if you use a specific font and text size on your site then this is the place to make them match.
The one thing that I am always strict about changing is the incredibly ugly blue link color. So I always change that to the “normal” blue color used on most websites. I was actually wondering what made this color the norm, and I realized that this is the color used by Google, so I guess they created the norm… The color Google uses is #1a0dab, but you can use #0000cd or #000080, which have slightly different tints of blue, but choose the color you like best, just please don’t keep the Mailchimp blue.
For the footer (much like the preheader) I like to the keep the link colors as neutral as possible. The reason for this is that most of the stuff in the footer is not that important or I don’t really want people to spend time in there. I would much rather have people spend time reading the content of the email and not looking through the unimportant parts of the email (especially the unsubscribe button.) Obviously, it needs to be there, but that doesn’t mean I want people to look at it.