Read Time: 9 min

Comcast Previews Now Live in Litmus: Discover How It Renders Email


We’ve listened to your feedback and are proud to announce that you can now instantly preview your emails in Comcast with Litmus! Here’s an introduction to Comcast and what you need to know about Comcast email rendering.

Comcast is a well known multinational media company, based in Philadelphia, USA. It’s the largest broadcasting and cable television company in the world, by revenue, and it first started providing Internet access way back in 1996. Currently Comcast has about 22.87 million internet subscribers, making it the largest Internet Service Provider (ISP) in the United States.

All of Comcast’s cable television, broadband internet, and VOIP telephone services sit under the Xfinity brand.

Comcast’s email addresses aren’t available to everyone. Only Xfinity subscribers can get access to a Comcast account. With each Comcast account you can have up to six email addresses.

Optimize your emails in Comcast

Use Litmus Email Analytics to see if your subscribers open in Comcast and get Instant Previews of the Comcast webmail client in Chrome, Internet Explorer, and Safari.

Try Litmus free →


As you need to pay for their ISP services, expect Comcast email address holders to be slightly older than users of other email clients such as Gmail or Yahoo! Mail, both of which offer email addresses for free.

With Comcast’s massive market share as an ISP and the fact that it has been around for a while, you shouldn’t be surprised to find subscribers with Comcast email addresses in your database—especially if your subscribers are mostly US-based. With both of these facts in mind, it’s important to be aware of how your emails will render in this client.

Let’s take a look at the Comcast email client, how it sorts emails, and how it displays your designs.

Inbox View

Comcast: Inbox View

The Comcast inbox is simple. Emails are sorted by the date that they arrived in the inbox. However, this can be personalized by the user—either seeing the oldest or newest email at the top of their inbox.

The first thing email marketers will notice is the preview text is not shown in the inbox view, but it displays numerous characters for the subject line. However, the user can change the width of the subject line column in the inbox view. While it looks like you can use up to 83 characters for your subject lines for Comcast users, this will vary depending on how the user has set up their inbox. The same is true for the sender name column.

With the lack of visible preview text, ensure your sender name is clear and recognizable, and your subject line is just as clear and engaging for your subscribers.

Inbox management

It’s not uncommon to see automatic sorting of emails in newer email clients, like Inbox by Gmail, placing promotional or transactional emails into different folders automatically. With Comcast’s inbox there is no automatic sorting. All emails, whether they’re personal, transactional, or promotional, will arrive in the same inbox (unless the user has set up any prior filters).

While this is a relief for many email marketers (automatic sorting can give us the nervous sweats), it does mean that your email will be fighting for attention among all sorts of emails that arrive in the inbox. This makes the sender name and subject line even more important.

How Does Comcast Display Email?

Double-clicking on an email in the inbox will open up the email within the same window frame. The user also has the option to view the email to the right or bottom of the inbox view.

Default inbox view with Reading Pane off
Default inbox view with Reading Pane off
Inbox view with Reading Pane to the right
Inbox view with Reading Pane to the right
Bottom Reading Pane
Inbox view with Reading Pane at the bottom

When viewed on the right you may find that users will have to scroll right to view the entire email, depending on how the user has set up their window frames. There is good news though—Comcast supports media queries! So, depending on how your media queries are set up, users who use the right-hand window view may see a version of your email that’s tailored for smaller devices/widths, rather than desktop. Something to be aware of if you’re hiding anything on your desktop “version” in your mobile “version.”

Users also have the option to “pop-out” the email into its own window. As this reloads the entire email, your email analytics may count these as multiple email opens.

How are images displayed?

Images are displayed by default on any email that’s opened in the inbox. However, this can be changed by the user in their preferences. When images are disabled, ALT text is not displayed and associated image styling such as background colors are also missing. All blocked images appear as large blank spaces.

No images

It’s still important to have ALT text in place for non-Comcast subscribers to ensure they have a great experience in images-off scenarios.

Emails that end up in the spam folder have images off by default, and display no ALT text or any styling associated with the image (background colors that are used as a fallback for missing images aren’t displayed either). Users have the choice to switch images on for any email in the spam folder, once the email is open. While we hope your emails don’t end up in the spam folder, it can happen. So make sure you have a healthy text-to-image ratio, as well as bulletproof buttons. This ensures that if it does end up in there, users will still be able to recognize your email and mark it as not spam.

Animated GIFS

You’ll be pleased to know that animated GIFs are fully supported within Comcast’s inbox! But remember there are still inbox providers out there (ahem Outlook) that don’t support animated GIFs. Knowing which email clients your subscribers use will help you make the decision on whether animated GIFs are worth the time and effort to create for your campaigns.

Background Images

It shouldn’t be too much of a surprise to learn that background images are not supported in Comcast’s inbox. Support for background images is patchy among email clients in general.

No background images
No background images
The same email with background images on

If you do choose to use background images in your emails, don’t use them for key areas which display important information, have a fallback background color, and don’t rely on background images for the overall look and feel of your email.

Web fonts

Like many email clients, web fonts are not supported in Comcast. For this reason, it’s good to view web fonts as progressive enhancements rather than an email design must-haves. Ensure you have web-safe fonts as your fallbacks if you are using web fonts in your emails.

Other Progressive Enhancements

It’s interesting to note that unlike a lot of basic inbox providers, Comcast does support some CSS3, including border-radius and CSS3 transitions.

CTA example

So if you’re using border-radius for your bulletproof buttons to give them that beautiful rounded button look, expect them to look great in Comcast’s inbox, too.

As mentioned above, CSS3 transitions are also supported. As a progressive enhancement, CSS3 animations such as transition can add great effects to rollovers or bulletproof buttons. So it’s great to see them supported in Comcast.

Working carousel with CSS3 transitions between image slides in carousel
the “flying” dots!
The “flying” dots!

Comcast quirks

As with a lot of email clients, expect to see some quirks within Comcast’s inbox.

Hovering over any text link or image that is linked to in an email in Comcast will display a hover showing the entire URL. This behavior could be seen as a security measure, so users are aware of where the links are taking them before clicking. The entire link will be shown in this rollover, no matter how long it is.


Another interesting feature of Comcast’s inbox is the ability to view the source of the email. Yes, your subscribers will be able to view the HTML source of the emails you’re sending them when opening in Comcast’s inbox (if they’re fellow #emailgeeks who are interested in that sort of thing!). While this doesn’t pose any real issues, if you have any comments in your HTML code that aren’t quite customer facing, it’d be a good idea to remove those before sending.

View-source link

Including a plain text version of your emails is a best practice even today when the majority of email clients in use don’t fall back to the plain text version. In Comcast, if the email received doesn’t have a plain text version included, “The message has no text content.” will display above the main HTML message.

Plain text

This could potentially distract your readers from your main message.

Think of this as a reminder to set up plain text versions for all your emails—you never know when not having them may cause an issue.

Optimize your emails in Comcast

Use Litmus Email Analytics to see if your subscribers open in Comcast and get Instant Previews the Comcast webmail client in Chrome, Internet Explorer, and Safari.

Rest assured that your designs look great regardless of where your subscribers are opening.

Try Litmus free →

Jaina Mistry

Jaina Mistry

Jaina Mistry is the Director, Brand & Content Marketing at Litmus