I do mailing list management using Campaign Monitor or Mailchimp. I can design your mailing list template and assist you in complying with the CAN SPAM act.
The reason email templates are not much fun to setup is due to the fact that there are so many ways of viewing said mail template, here the device has an impact as well as OS and browser software. The fact is their is no defined standard and every mail software has its quirks.
Template Width – 550 – 650 pixels
You can go wider but this does lead to limitations in visibility in mobile browsers and older mail clients. As mobile viewing is on the increase it is best to keep to 600px width.