HTML email best practice guidelines

By Katrina Makins | 19 Mar 2019

Email is one of the most long-lived and valuable digital marketing channels for businesses, with 59% of marketers noting that emails deliver the highest ROI for them. Currently, there are over 3.7 billion email users in the world and that number is expected to grow to 4.1 billion by 2021. With two thirds of customers admitting that they’ve made a purchase as a direct result of a marketing email, it’s crucial that marketers get their email strategy right, starting from the basics.

Size matters

We live in a time where emails are opened on any device, browser, and email provider, so marketers need to think about size when creating an email template. Here are some core rules to follow:

  • Subject lines and preheaders should always be under 65 characters to make sure they fit nicely and are readable no matter what the email client is
  • Use good quality, crisp images – but make sure they’re optimised so load times aren’t compromised by adding them at a resolution below 72 dpi
  • Emails shouldn’t be wider than 600 pixels so there’s no need to scroll from side-to-side, making content easily readable.



Our attention span is decreasing, which inevitably affects how we want to consume content. To engage and maintain users’ attention, it’s important to follow the below measures when designing an email template.

  • Having a maximum of 600 pixels in width to work with, means that emails shouldn’t have more than two columns in order to maintain some visual impact – I dare you to have the patience to side scroll on your phone screen.
  • Keep images to the left and text to the right – our eyes are primarily attracted by images rather than text, so keeping images on the left side of the email will allow the visual element to be the first one to be seen and to capture the reader’s attention, who can then move on to read the text.


Call to actions

Call to action buttons (CTAs) are key to incite engagement in any type of email, so it’s important that marketers get them right – here are my tips:

  • Make sure the CTA stands out from a visual perspective and that it’s clear and it’s clickable
  • When determining what dimensions to have for a CTA, always consider how visible and intuitive the button is, particularly for mobile phone users or people with visual impairments
  • Don’t be afraid to repeat the CTA at top and bottom of the email if there’s a lot of copy; this will make it easily accessible as the reader scrolls through the content



When it comes to email content, there are a few guidelines to keep in mind:

  • Use HTML text, especially if your email includes a lot of copy in areas, as it’ll ensure your email content is easily legible across devices
  • Where possible, avoid background images, as these are turned off 43% of times – alternatively, keep imagery and layout as simple as possible using a plain grid layout
  • If you’re including imagery, always add in alt text to give some context to the reader in case the image is blocked

Overall, marketing emails can achieve a multitude of goals – from creating awareness and promoting products or content, to lead generation and sales. Regardless of the end goal, it’s pivotal that the basics are firmly in place in order to really engage and tighten relationships with audiences.