I'm using the Basic with Logo template for my email blasts, and even though it shows up alright in the draft preview, when I send a test email the image is giant. I don't want to mess with the email template code, but how do I make the logo image smaller?
If you want to set the size of your logo in the header of your email blast, the easiest way to accomplish this is to use the "Basic" email template instead. Then, you can upload your logo image into the Files tab of your blast and insert it as a regular image above your salutation.
If you want to make the image responsive depending on the size of your recipient's screen, you can set the dimentions of the image to a percentage, rather than a fixed pixel amount - as shown in the screenshot below.
Complete and current information on how to use NationBuilder is available in the documentation section.