Is there any UX study on when we should send HTML email and when plain text?

Question

By considering email web and desktop client's compatibility and big/small screen and devices. Is there any UX study on when we should send HTML email and when plain text?

For better conversions.

Answer 1

While I havent been able to find specific research on what works best for conversion,Here are a couple of factors you should consider

1. What are the emails clients your users are using : Though most mail clients allow you to see HTML based emails, the main challenge is the rendering of HTML is different for different email clients. So if you are confident about your demographics and are sure that the email clients would render the emails correctly, HTML emails can help convey your emailers in a much richer way but while dealing with email clients with limited or varying support of CSS, you need to think about how to best present an uniform experience to users. To quote this article from hubspot

Some Browsers, Email Clients & Mobile Devices Can't Handle HTML

As the infographic reminded us, because of factors like bandwidth and functionality, not all email clients, browsers, and mobile devices that support email are sophisticated enough to display formatting like HTML properly. When marketers fail to optimize their email for both versions, what happens is a broken design and an undecipherable, ineffective email.

2. What is the focus of your newsletter or email :Your choice of email options would be defined by the focus of your email. If the email has a simple focus like informing the user that an order has shipped and this is the tracking number, a plain text email will just fine but if you are trying to make a strong pitch with images and multiple call to actions, then an HTML email will work.

However please note that emails can be blocked by the email client and reliance on only images can actually proved detrimental and have your email look like this

As stated above if your call to action is simple and singular in nature, a plain text email would help just as well

Here are a few links for you to read

25 Compelling Statistics About the Importance of Email Marketing

Plain Text versus HTML Emails - What's Your Opinion?

How Your Customers Actually Read Your Emails