Inserting a horizontal line in Outlook messages helps separate sections of your email for better readability. If you have ever wondered how to insert a horizontal line in Outlook, this guide covers every method across desktop, web, and mobile versions. Whether you are composing a formal business email or a casual note, a simple line can make your message look organized and professional.
Horizontal lines act as visual dividers, breaking up long blocks of text. They are especially useful for separating an introduction from a call to action, or for distinguishing different topics in a single email. Below, you will find step-by-step instructions for Outlook 2016, 2019, 2021, Microsoft 365, Outlook on the web, and the mobile app.
How To Insert A Horizontal Line In Outlook
This section covers the primary method for adding a horizontal line in the desktop version of Outlook. The process is straightforward and works across most recent versions.
Using The Horizontal Line Button In The Ribbon
The easiest way is to use the built-in horizontal line tool. Follow these steps:
- Open a new email message or reply to an existing one.
- Place your cursor where you want the line to appear.
- Click the “Insert” tab in the ribbon at the top of the message window.
- In the “Symbols” group, look for the “Horizontal Line” button. It looks like a thin, straight line.
- Click the button. A horizontal line will be inserted at your cursor location.
If you don’t see the button immediately, you might need to expand the “Symbols” group. In some versions, it is hidden under a drop-down menu. Once inserted, the line spans the full width of your email body.
Customizing The Horizontal Line
You can change the line’s appearance after inserting it. Right-click on the line and select “Format Horizontal Line.” A dialog box appears where you can adjust:
- Width (percentage or fixed pixels)
- Height (thickness)
- Color
- Alignment (left, center, right)
Experiment with these settings to match your email’s design. For example, a thinner, gray line looks subtle, while a thick, blue line draws attention.
Using Keyboard Shortcuts
If you prefer typing over clicking, you can use a keyboard shortcut. Type three hyphens (—) and press Enter. Outlook automatically converts them into a horizontal line. This works in the email editor as long as AutoFormat is enabled. Other shortcuts include three underscores (___) or three asterisks (***) for different line styles.
Note that this shortcut only works in the desktop version, not in Outlook on the web or mobile. Also, if you type the characters and press Enter but nothing happens, check your AutoCorrect settings.
Alternative Methods For Different Outlook Versions
Not everyone uses the same Outlook version. Below are methods for Outlook on the web, the mobile app, and older desktop versions.
Outlook On The Web (Outlook.com Or Office 365 Web)
Inserting a horizontal line in the web version is slightly different. There is no dedicated button, but you can use the “Insert” menu or a workaround.
- Open a new message in Outlook on the web.
- Click the “Insert” tab in the formatting toolbar.
- Select “Horizontal line” from the drop-down menu.
- The line appears at your cursor position.
If you cannot find the option, try using the “Border” tool. Highlight a blank line, go to the “Format” tab, and click “Borders.” Choose “Bottom border” to create a line that looks similar. This method gives you more control over thickness and color.
Outlook Mobile App (IOS And Android)
The mobile app does not have a direct horizontal line feature. However, you can still add a visual separator using these steps:
- Type a series of dashes (like ———) and press Enter. The app may not convert them automatically, but the dashes serve as a simple line.
- Use the “Insert” menu if available. In some app versions, you can find “Horizontal line” under the “Insert” icon (usually a plus sign).
- Copy a horizontal line from a web page or document and paste it into your email.
For a more polished look, consider using a table with a single cell and a bottom border. This is a bit advanced but works well for mobile users.
Outlook 2010 And 2013
Older versions like Outlook 2010 and 2013 also support horizontal lines. The process is similar to newer versions:
- Open a new email.
- Click on the “Insert” tab.
- Find the “Horizontal Line” button in the “Illustrations” group.
- Click to insert.
In Outlook 2010, the button might be labeled “Shapes” instead. If so, select “Line” from the shapes menu and draw a straight line across your email. This method requires manual adjustment of length and alignment.
Common Issues And Troubleshooting
Sometimes the horizontal line does not appear as expected. Here are solutions to frequent problems.
Line Not Showing In Email
If you insert a line but it does not display, check your email format. Outlook supports horizontal lines in HTML format. If your message is set to plain text, the line will not render. Switch to HTML by going to “Format Text” tab and selecting “HTML.”
Also, ensure your recipients’ email clients support HTML. Most modern email services do, but some older systems may strip out formatting.
Line Appears Too Thick Or Thin
Adjust the line’s height in the “Format Horizontal Line” dialog. If you used the keyboard shortcut, the default thickness might be 2 pixels. Right-click and change it to 1 pixel for a thinner line, or 5 pixels for a bolder one.
Line Breaks Or Disappears When Sending
This can happen if you use a custom line style that is not compatible. Stick to the default horizontal line or use a simple bottom border on a paragraph. Avoid using images as lines, because they may not load for all recipients.
AutoFormat Not Working
If typing three hyphens does not create a line, go to “File” > “Options” > “Mail” > “Editor Options” > “AutoCorrect Options.” Under “AutoFormat As You Type,” check the box for “Border lines.” This enables the shortcut.
Best Practices For Using Horizontal Lines In Emails
Horizontal lines are useful, but overusing them can clutter your message. Follow these tips:
- Use lines sparingly. One or two lines per email is usually enough.
- Keep lines thin and neutral in color. Black or gray works best.
- Place lines between distinct sections, not within paragraphs.
- Test your email in different clients before sending important messages.
- Combine lines with white space for a clean layout.
For example, you might use a line after your greeting to separate it from the main content, and another line before your signature. This creates a professional structure without looking busy.
Advanced Techniques For Power Users
If you need more control, consider these advanced methods.
Using Tables For Custom Lines
Insert a one-row, one-column table. Set the table borders to show only the bottom border. This creates a horizontal line that you can color, resize, and position precisely. To do this:
- Click “Insert” > “Table” and select a 1×1 table.
- Right-click the table and choose “Borders and Shading.”
- Remove all borders except the bottom one.
- Adjust the width and color as needed.
This method is more flexible than the default horizontal line tool. You can even add text above or below the line within the same table cell.
Adding Lines With CSS In HTML Emails
If you write HTML emails directly, use the
tag. For example:
<hr style="border: 1px solid #ccc; width: 100%;">
This creates a clean, thin line. You can customize the style, color, and width. Note that some email clients strip out CSS, so test thoroughly.
Using Signature Lines
Some users insert a horizontal line as part of their email signature. In the signature editor, you can add a line using the same methods described above. This ensures every outgoing email has a consistent separator below your name.
Comparing Methods Across Platforms
Here is a quick comparison of how to insert a horizontal line in Outlook across different platforms:
| Platform | Method | Ease of Use |
|---|---|---|
| Desktop (Windows/Mac) | Insert tab > Horizontal Line button | Easy |
| Outlook on the Web | Insert menu > Horizontal line | Moderate |
| Mobile App | Dashes or paste from elsewhere | Hard |
| Older Versions (2010/2013) | Insert tab > Shapes > Line | Moderate |
Choose the method that matches your version and comfort level. For most users, the desktop button is the fastest and most reliable.
Frequently Asked Questions
Here are common questions about inserting horizontal lines in Outlook.
Can I insert a horizontal line in Outlook for Mac?
Yes. In Outlook for Mac, go to the “Insert” menu and select “Horizontal Line.” The process is similar to the Windows version.
Why does my horizontal line look different after sending?
Different email clients render HTML differently. Test your email by sending it to yourself first. If the line looks off, use a simple border instead of the default horizontal line.
Is there a way to insert a horizontal line without using the mouse?
Yes. Type three hyphens (—) and press Enter. This keyboard shortcut works in most desktop versions of Outlook.
Can I add multiple horizontal lines in one email?
Absolutely. You can insert as many lines as you need, but keep readability in mind. Too many lines can make the email look fragmented.
Does the horizontal line work in plain text emails?
No. Horizontal lines are an HTML feature. If you send a plain text email, the line will not appear. Switch to HTML format for best results.
Final Thoughts On Using Horizontal Lines
Mastering how to insert a horizontal line in Outlook is a small skill that improves your email communication. It helps readers scan your message quickly and understand its structure. Whether you use the button, keyboard shortcut, or a workaround, the key is to keep it simple and consistent.
Remember to test your emails before sending them to a large audience. A broken line can look unprofessional. With the steps in this guide, you can confidently add horizontal lines to any Outlook message, on any device.
Now you have all the tools to organize your emails effectively. Try inserting a line in your next message and see the difference it makes.