Are you experiencing an issue with thin horizontal lines appearing in your emails when sending through Outlook? These lines can make your emails look unprofessional and disrupt the reading experience. Learn troubleshooting steps to fix these lines.

You spend time, love, and energy perfecting your emails. Why does Outlook have to throw this wrench into your plans? These random lines appearing in your emails are a pain that is common across Outlook. We’ll cover some options to get rid of those pesky lines for good.

Why Do Thin Lines Appear?

This issue has been around for a while, but Microsoft has not confirmed why it happens. We know it occurs in Outlook specifically, and it’s not limited to any email-building platform.

There are a few theories on why it’s happening, but the most prevalent one seems to be an unaddressed UI bug that results in the HTML not rendering properly.

The notorious horizontal line in question:

When Are Thin Lines Likely To Show Up?

There are a few scenarios we see the horizontal lines occur in time and time again.

• • Different-sized content blocks

Content blocks of varying sizes that don’t line up well may cause horizontal lines to appear. 

• • Zooming in on Outlook Desktop: 

These lines are commonly visible when users are zoomed in on the email, as 1px spacing is relative to the device view.

• • Stacked image borders

Outlook will sometimes add a border surrounding an image or element if you have several images on top of each other. Ensure borders are set to 0 to avoid this.

• • Your image size is uneven

Ensure your image size is divisible by two with no decimals to ensure no stray pixels. For example, opt for an image that is 200 px by 200 px, rather than 205px by 205px. There are lots of free image editors that can help adjust pixels!

• • Your emails are being forwarded

The original email can look totally fine, but a forward can make the lines appear out of nowhere. This is because forwarded emails are sent outside of ContactMonkey (through Outlook) and our system can’t reformat the HTML.

Avoiding Thin Lines In Outlook Emails

Now that we know most of the whys and whens of this Outlook annoyance, let’s talk about how we can avoid them.

There are a few ways we can avoid white lines showing up in your emails:

1. Get up to date
2. Match the background
3. Add an empty row
4. Keep all numbers even
5. Simplify your email
6. Break it down

Get Up To Date

Microsoft seems to have fixed its most recent version of Outlook to drastically reduce the appearance of these lines. Anyone who has turned on "Try the new Outlook" in their Outlook instance will find that they no longer see the horizontal lines.

It's important to note that this works only if both you and the recipient has turned this on, but it's promising headway from Microsoft.

Match The Background

By setting your email's background color to the color of the lines appearing (often white or dark), you can minimize the appearance of the horizontal lines. This applies to your content background color and even your table's background color.

To change your emails background color, follow these steps:

1. Sign in to your ContactMonkey dashboard
2.  Head to Emails 
3. Create your new email or open up the email you want to edit
4. In the menu on the left, select Settings
5. Under Background color or Content area background color , enter your desired color hex code or select from the color wheel.

Background color: the default background color for the design. You will be able to override it at the row, column, and content block level when settings properties for those elements.

Content area background color: the default background color for the content area only.

Learn more about editing your email settings in Edit Default Settings Within The Email Builder.

Add An Empty Row

Adding an empty row or increasing padding in the row above by 1px may help with balancing pixels across the email. To add a row to your email, follow these steps:

1. Sign in to your ContactMonkey dashboard
2. Head to Emails
3. Create your new email or open the email you want to edit
4. Click on Rows in the menu on the right
5. Drag and drop a new row into your email 

Keep All Numbers Even

For some folks, the fix is as simple as changing font sizes from odd numbers to even numbers. For example, if you have a font size of 13px or 15px, try converting it to 14px.

You can also try manually changing heights, font sizes, and line-heights to achieve the same outcome.

We also recommend ensuring that image pixel sizes are divisible by two with no decimals to ensure no stray pixels. For example, opt for an image that is 200 px by 200 px, rather than 205px by 205px. There are lots of free image editors that can help adjust pixels.

Break It Down

Breaking down large content blocks into smaller blocks using rows tends to help minimize any horizontal lines. 

Learn more about how to use rows here.

Resources Used For This Article

Fixing White Lines in Outlook

How Do I Get Rid of the Lines in Outlook Emails?