In this article we will discuss some of our most frequently asked questions for rendering problems in Outlook. If you notice an issue that sounds similar to what you are running into, try the suggested fixes below to see if this resolves the issue. If the issue still persists after following the troubleshooting steps, reach out to our Knak Support team and we'd be happy to provide further guidance.

For maximum compatibility across email clients, Knak will prevent you from adding any borders that is thicker than 8px. This is to prevent unexpected rendering differences between Outlook Classic and other email clients.

In Microsoft Outlook for Windows, borders will only ever display up to a maximum of 8 pixels wide. Even if you set a border to be much higher in your layout, it will revert down to a width of 8 pixels when rendered in Outlook for Windows.

This is caused by a limitation built into Microsoft Word. Outlook uses the same rendering engine as Word to handle the editing and display of layouts, and Word only allows borders to be a maximum of 6 points wide, which converts to 8 pixels.

Unfortunately it’s simply a strange limitation of the software, and you’ll see it when applying borders in Word too.

Knak uses a coding technique called Vector Markup Language (VML) buttons in order to ensure your buttons look great across all email clients, including Outlook. This technique essentially creates two versions of the button. The first uses a conditional comment to target Outlook desktop clients and uses VML markup in Outlook specific code to style the button (round corners).

There are some instances where VML will be disabled on your buttons in Knak. When this is the case, your buttons will display with square corners in Outlook, because Outlook only supports the rounding when VML is used.

Some instances where VML buttons will be disabled are:

As a first step for this, make sure you have applied a valid link to the button (including the https://) or if using a token make sure you are syncing your email to your MAP before sending a test email so that the link populates correctly upon send.

If your button does not have a proper link added to it, some versions of Outlook will not render the button.

Similar to the issue above, the problem is the fact that when you forward an email, a lot of styling gets lost in the process. Each email app (and service) will do it differently. Some email clients (especially Outlook and Gmail) change or sanitize parts of the original HTML when you forward a message. Outlook tries to “clean up” forwarded emails which often leads to rewriting tables, flattening VML, removing styles, and killing links.

We have a feature that can be enabled in your account to optimize HTML for forwarding which we have to try to prevent the above issues; however, we cannot avoid it as each client treats forwarded emails differently.

Since most email clients rewrite forwarded content heavily, we recommend using "Forward to a Friend" tokens where possible. Another way to mitigate this is for us to enable non VML buttons which means button corner’s won’t be rounded in Outlook, but will allow your buttons to be clickable.

Outlook doesn’t support images on Nested Lists. If you use one, it will display in all email clients except Outlook, and Outlook will display a plain fallback bullet for the Nested List items.

Different versions of Outlook have different default behaviors for how the email client will change the colors in dark mode, but overall the email client doesn’t support dark mode editing.

And for further assistance, check out this video for an overall crash course on best practices for dark mode editing:

We automatically apply some fixes aimed at improving rendering in Outlook’s Dark Mode. For example, we automatically apply the popular “MSO gradient textfill” solution to white or black text inside CTA buttons. Unfortunately however support varies for this solution, and its effectiveness can change with different Outlook updates.

In short, we do provide code in Knak to override dark mode styles as much as possible, but the larger issue lies with it not supporting dark mode editing options.

In Knak we make use of custom webfonts to help our clients get as close to their brand guidelines as possible in their email content. These custom webfonts always have a fallback "web safe" font that is similar in style to the custom font. This is because not all email clients will be able to render the custom web font and will show the fallback instead.

Custom web fonts are not generally supported in any versions of Outlook, so in almost all cases, users will see the fallback fonts. Some users of Outlook for Windows may be able to see a custom web font if it is listed in the Microsoft Cloud Fonts list, but not all installations of Outlook support this.

This issue can occur with photos taken on smartphones. Some smartphones save landscape (wide) photos as if they are portrait (tall) and note in the image metadata that the photo is ‘rotated 90º’, or vice versa. While all modern devices and email clients will display the image correctly, Outlook for Windows cannot read the rotation information in the metadata, causing the image to appear sideways.

Opening and re-saving the image will permanently apply the correct rotation to the image to solve the issue.

You can quickly do this in Knak by clicking the Edit icon to open the image editor (shown below). Without adjusting anything, simply click Save. After saving, the image will be fixed.

Note: Microsoft is releasing a completely overhauled version of Outlook over the next few years (which uses the Outlook.com rendering under the hood) which will completely remove this issue.

Outlook and Gmail often automatically underline text that looks like a link (e.g., addresses, phone numbers). Always add real links using Knak’s link tool to avoid this issue.

You can find more information in this help document: https://help.knak.io/en/articles/9628546-known-issue-gmail-and-outlook-automatically-underlining-links

If you are testing an email and notice a rendering issue in your email inbox that you do not see in the Knak email testing feature or in external platforms such as Email on Acid or Litmus, check to see if you can spot a banner at the top of your Outlook email that says “WARNING: This email originates from outside your organization” or “CAUTION: External sender.”

Many B2B organizations nowadays like to implement additional security software that scans all emails that come into an organization from external senders. The way these security systems work, is by intercepting the email before it arrives in the email client, investigating its contents, in some cases modifying it, and then delivering it in its changed form.

*Important to note: This only affects users who are opening their emails in an environment where all their emails have been quarantined and pre-opened, and this affects all emails received by that person from “external” senders, not just Knak emails. These processes are instigated and completely controlled by the organization doing it: we have no visibility into what they are doing or how to ensure our HTML is compliant.

Recommended solution:

See if the email address can be added to your “Safe senders” list by your IT department. For example, if the Knak test emails have the issue, ask to have our knak.com domain added to their safe senders list so this modification won’t happen to our emails.

The white line issue looks something like this:

These white lines are caused by a glitch with how Outlook scales content on screen. Office products were originally intended for the creation of printed documents, so they use points (pt) rather than pixels (px) as measurement units. They convert any pixel values to points on the fly when displaying on-screen content.

Sadly it’s not possible to completely avoid the issue, only to mitigate it. Check out this help document for helpful tips on how to mitigate this issue: https://help.knak.io/en/articles/9421305-outlook-issue-white-lines

Note: Microsoft is releasing a completely overhauled version of Outlook over the next few years (which uses the Outlook.com rendering under the hood) which will completely remove this issue.

Need more help? Contact support via live chat within Knak using the chat bubble in the bottom right corner or email support@knak.com