Who this checklist is for:
You should use this checklist if you want to ensure that people using different computers, browsers, and devices can all successfully read your email blasts in the way you intended.
Do keep it as simple as possible
Even relatively uncomplicated things like tables or changing fonts can make an email render incorrectly on some platforms. Always ask yourself whether adding more complicated formatting or content is strengthening your message. If you absolutely have to have the fancy stuff, consider making a screenshot of it, including that image in the email, and then linking to the more complex version on your website.
Do use in-line CSS (and not an external style sheet)
Referring to an external CSS file in your email template is a bad idea. Many email programs will refuse to load the external CSS, meaning your email blast won't look very nice at all. You can accomplish most of the same things with internally-defined styles in your template. The things you can't do probably should not be done in an email blast anyway (see "Keep it as simple as possible" above.) You can use an inline styler tool like this one to make your CSS inline.
Do send test messages to as many platforms as possible
So you sent a test message to yourself, it looked fine, and you sent out the email blast. And then that one nice lady on the board of directors sends you a vicious email asking why the organization's e-newsletter looks all ganked up on her Yahoo Mail.
You can't please all the people all of the time, but it's worth sending test emails to at least a couple of different addresses to see how it looks on different platforms. If you've got the time, try your work/main email, Yahoo mail (which is notorious for messing up certain formatting), and a mobile device.
Do resize images to a smaller size before uploading them to Salsa
You got a fantastic photo from one of your field organizers, so you upload it straight into Salsa. It looks a little big when you add it to your email blast, so you just tell Salsa to shrink it a little bit, and you're good to go, right?
Nope. Image files can be huge, and loading huge images in your email blast can make the blast look broken, or even make it undeliverable (or worst of all, marked as spam). Note that just telling Salsa to resize the image won't actually make the file size smaller, it'll just change how the image appears. To fix this, use a program like Mac Preview or Windows Paint.net to resize the image and save a version in a smaller size. This will reduce the file footprint and make things work better across platforms. Learn more about resizing images here.
Don't paste content directly from Word.
Yes, we talk about this a lot at Salsa. We've been talking about it for years. And Salsa's gotten better about dealing with Word, but it's still a no-no. You may get the text to paste nicely, but images and other formatting with either not paste right or will break everything in sight.
Remember: friends don't let friends paste from Word. True friends always copy from Word, paste into a plain text editor like Notepad (PC) or TextWrangler/TextEdit (Mac), and then copy/paste from the plain text version into Salsa. You'll lose things like italics/boldface and fonts by doing this, but it's good practice to adjust your workflow and email templates to minimize the need for such formatting. Hint: in a desperate hurry and don't want to reformat things? Paste from Word into Google Docs, then paste into Salsa. Still has some issues, but works okay in a pinch.
Don't try to embed or attach things to email blasts
It sounds silly, but it's amazing what people will try to squeeze into an email. Animated .GIF images, YouTube videos...yeah. A person once asked whether it was possible to have a Flash animation pop up when someone opened the email. Our response: if it were possible (it's not), and if such a thing wouldn't immediately land your email on every spam blacklist in the universe (it would), suppose for just a moment that you did indeed send an email blast with a Flash popup in it. Within moments you would have an angry torch-bearing mob outside your office. And they'd be justified. Really, just stick to images and nice HTML formatting. It gets the point across and it won't break anything.
Don't use cute fonts like Comic Sans, OR TYPE IN ALL CAPS
USING ALL CAPS IS TERRIBLE. IT'S HARD TO READ, IT'S THE TEXT EQUIVALENT OF SCREAMING, AND IT'S ALMOST GUARANTEED TO GET YOUR EMAIL SENT TO EVERY SPAM FOLDER IN EXISTENCE. DON'T DO IT, EITHER IN YOUR YOUR SUBJECT OR THE BODY OF THE MAIL.
Not quite as terrible but still worth noting: nothing good can come from using Comic Sans or similar "cutesy" fonts. I mean, it'll work and it won't get you Spam-blocked, but it sends the message that you shouldn't be taken seriously. Unless your message has something to do with young children's birthday parties, please use a different typeface.