Some people think that email is email, but for savvy marketers and tech gurus, the difference between HTML and plain text email is quite drastic. The best way to visualize the differences is to consider what text looks like in MS Word versus what it looks like in Notepad. Notepad is akin to plain text, while Word allows for rich text format in the same way HTML does. Like Word, most people just use HTML email and never think twice about it. However, there are good reasons for taking the time to consider the differences between the two, particularly now that mobile email clients are so common.
 
HTML Email Uses and Benefits
HTML is used by the majority of people to send and receive emails. Even when you don’t do much to “dress up” an email with HTML, you are still using it in most cases. For instance, creating a hyperlinked word or inserting a picture into an email requires HTML. Of course, changing font sizes, using bold, changing text color, or inserting company logos all require HTML.
 
By and large, consumers respond better to HTML than to plain text, which is just one of its benefits. HTML also provides you with the ability to:
Track open rates of an email (did the recipient open it or not)
Include images
Format text using center, justify, etc.
Include forms
Make links clickable
Break up an email into columns, headers, etc.
 
Drawbacks of HTML Email
So there are a lot of benefits to using HTML in email, which naturally begs the question “why doesn’t everyone use HTML all the time?” It turns out that HTML has some drawbacks that can make it less desirable in some situations. First among the drawbacks is the fact that HTML does not look the same in every email client. An HTML email that looks great to one person may be distorted or unreadable to another. HTML also suffers from the following problems.
It has longer load times
It feels less “personal” to the recipient
Only about 75% of recipients can view HTML. The ability to view HTML is especially limited on mobile devices. If an email client cannot display HTML, it will render the email with text and mark-up all in one big glob, which makes the email very hard to read.
It is subject to heavy spam filtering (email clients will see HTML-only email as potential spam and may block it)
It is often recognized as an “advertisement” by readers and immediately dismissed.
 
So, HTML email is a mixed blessing at best, which brings us to text-only emails. Like HTML, text-only or plain text emails have advantages and disadvantages.
 
The Benefits of Plain Text Email
Plain text email is the simplest to produce and often the easiest for consumers to read if the message is short. It benefits from the fact that every email client can render it correctly and that it is easily viewable on the small screens and limited browsers of mobile devices.
 
Plain text is also less likely to be caught in a spam filter inadvertently. Because it is unembellished, there is little risk of viruses from plain text email and thus people are less wary about opening it. Unfortunately, plain text email has a number of limitations.
 
The Limitations of Plain Text Email
First and foremost, plain text email cannot display hyperlinks, which means that an entire URL must be added to ensure that a recipient can copy and paste the link to a browser. It is true that some email clients will create the hyperlink once the email is open, but this is not always the case. Here are a few other drawbacks to text-only email.
Individuals words cannot be hyperlinked
No graphics
No formatting options
It is not possible to track open rates
 
The last point above deserves some attention because even though you cannot track open rates, you can add clickable tracking to plain text email. Though this is not the same as an open rate, a person who clicks through to a link will have necessarily opened the email, so you will get some idea of the open rate.
 
The Best of Both Worlds
It is true that plain text email is more readable on mobile devices, which will influence how much such emails are sent. It is also true that most people prefer formatting that can only be gained through HTML. However, one need not limit himself to just text or just HTML. In this case, it is possible to have your cake and eat it too.
 
Most email clients allow you to send both plain text and HTML emails together as one. The recipient’s email client can then determine which to display, which is especially important for mobile devices. If the client cannot display HTML, then it will use plain text. When sending email that is both HTML and plain text, it is important to keep the follow caveats in mind.
 
The text and HTML must be similar to one another. If the text part of the HTML is drastically different from the text of the plain email, then most email clients will mark it as spam. This occurs because spammers, recognizing that HTML is more likely to be flagged as spam, will include plain text as well to try to bypass filters. However, their laziness leads them to just put anything in the plain text section and most email clients pick up on this.
HTML formatting should be kept simple. Most people like a little formatting, but not a lot. Too many pictures, graphics, fonts, colors, and other clutter will make an email hard to read. The best use of HTML is for including company logos and creating headings, columns, and other formatting that makes the document easier to read. By way of analogy, some people point out that company letterhead is better than plain white paper for communication to clients. This is quite true. It is also true that fliers and outrageous junk mail seldom attract clients. This is no different for email. Use HTML, but keep it simple. Yes, this is a long point, but well worth making.
When in doubt, send plain text as it is guaranteed to be visible on all email clients.
If you are a business, test both and see what your clients prefer. New clients tend to prefer some formatting and graphics to pique their interest. Established clients prefer plain text because it feels more personal and thoughtful.
 
So there you have it. You can have the best of both worlds when it comes to email, but if you have to choose, you should error on the side of plain text. The old “keep it simple stupid” analogy rings loud and clear for email. Simple, tasteful emails will always win out over gaudy, overwrought monstrosities.