HTML email uses a subset of HTML 4.0 to provide formatting and semantic markup capabilities in email that are not available with plain text.
Most graphical email clients support HTML email, and many default to it. Many of these clients include both a GUI editor for composing HTML emails and a rendering engine for displaying received HTML emails.
It allows the sender to properly express quotations (as in inline replying), headings, bulleted lists, emphasized text, subscripts and superscripts, and other visual and typographic cues to improve the readability and aesthetics of the message, as well as semantic information encoded within the message, such as the original author and Message–ID of a quote.
Although HTML email development follows some conventions of regular website development, we have to consider the display criteria within email clients and webmail clients from all popular webmail providers, as well as supporting requirements for those across all of our supported browsers.
Users should be provided with a hyperlink so they can view the email as a web page. The code for this will vary depending on what level of personalisation is used.
Plain text email
A plain text version of any HTML email must be created and both offered to users. When delivering the email, your chosen distribution system will decide depending on the recipients‘ preferences which version they receive so you will not have to worry about how to target different clients.
Plain text emails are to be written in Notepad or similar, should contain no formatting at all and be 70 characters per line to ensure they display correctly in the preview pane.
Any marketing emails must offer an unsubscribe hyperlink or email address to users so they can be removed from mailing lists.