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How to Email Large Files as Attachments in MS Outlook

This post is part of a series called How to Use Microsoft Outlook (Essential Tutorial Guide).
How to Organize Your Outlook Contacts
What Is MS Outlook? (Pro Email Software Tool)

Whether you're sharing photos, reports, or other documents--sending attachments through Microsoft Outlook email is a convenient way to get files to others. But if you try to email large files using Outlook email you might run into trouble. That's because there's a default Outlook file size limit.

What is the limit for an Outlook email attachment? The email system defaults to 20 MB. If you try to send a larger file or a group of files totaling more than 20 MB, you'll likely receive an error message. Fortunately, there are ways to get around the Outlook file size limit if you know what to do.

In this tutorial, we'll examine the Outlook attachment size limit closely. You'll learn the basics of sending Outlook email attachments. And we'll discuss workarounds for how to email really large files using MS Outlook.

How to Email Large Files in Outlook (Video)

Start with the quick video screencast below or dig into the written tutorial instructions that follow. Learn how to work with Outlook attachments and zip your files are share them through Microsoft OneDrive.

Before reading on, consider signing up for the Tuts+ Business Newsletter. Get great email strategies in our free ebook: The Ultimate Guide to Inbox Zero Mastery.

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Now let's take a closer look at how to email large files using Outlook:

1. How to Attach a File to MS Outlook

Before you can attach large files to your MS Outlook emails, you need to understand the basics of attaching a file to a message. Let’s review that process:

Step 1. Create a New Message

To start, open Microsoft Outlook and create a new message:

Create a new message
Create a new message in Microsoft Outlook.

Type the text of your Outlook email message. You’re now ready to attach a file.

Step 2. Attach the File

From your new message, click the Attach File icon in the ribbon. A list of items you’ve used recently appears. If the file you want to attach isn't on the list, scroll to the bottom and click the Browse this PC option. File Explorer opens. Navigate to the file you want to attach to your Outlook email:

File attachments for Outlook Email
Find the file you want to attach to your email.

Click on the file you want to attach to your email to select it. Then click the Insert button. The file is attached to the email. You’ll see the file beneath the email subject line (in this case, a thumbnail of the photo I attached):

Outlook email with attached file
An Outlook email with an attached file.

Step 3. Send the Message

Once you’ve attached the file, review the text of your message carefully. Then click the Send button on the left to send your message.

2. How to Deal With Large File Attachments in MS Outlook

While it’s easy to attach a file to an MS Outlook message, there's an attachment size limit of 20 MB. If you exceed the Microsoft Outlook attachment size limit, you’ll get an error message:

Outlook File Attachment Size Limit error
If the total file size of all the files you've attached to your email exceed the attachment file size limit, you'll get an error.

The attachment file size limit is cumulative. So, in the example above, the error message appears when an additional file is being attached. Even though none of the files attached exceed the limitation by themselves, they total over 18 MB. The additional file is another 4 MB—making the total attachments over 22 MB.

In addition to the Microsoft Outlook attachment file size limit, it’s important to remember that some mail providers have a limit on the size of attachments their system will receive. So, if your email has a large attachment (or multiple attachments), your message may not be delivered.

There are several methods to get around Outlook attachment file size limitations, including:

  1. Using automatic resizing. Outlook offers automatic resizing for image attachments. 
  2. As a zip file. Zip files are especially useful if you've got more than one file to send. 
  3. Through Microsoft OneDrive. Microsoft offers cloud storage to anyone with a Microsoft account.

Here are instructions on how to use each of these methods:

Method 1. Use the Outlook Automatic Resizing

If you're using image file attachments, you can use Microsoft Outlook’s automatic resizing feature to reduce the size of the image. To use the feature, click the File tab on the top left of your message window. You’ll see the following screen:

Resize large images in Outlook
You can automatically resize large image files in MS Outlook.

Click the toggle button to the left of the Resize large images when I send this message to have Outlook automatically resize your image files.

Note: The image files are resized when you click the Send button. So, in the example above you still wouldn’t be able to add the additional file.

To get an idea of how much the image sizes were reduced, here’s a look at the sent message:

Images have been resized in Outlook
Outlook has resized the images attached to this email.

As you can see, even the largest file which was 5 MB, Regional (6).jpg, is now only 284 KB (.277 MB).

The automatic resizing feature only works when the photo images are attached to your email message and sent. If you’ve embedded the images into your message, they can’t be resized using this method. So, you won't be able to send a large image file with this method. But it can reduce the size of the images you're sending, which increases the likelihood that they'll be accepted by the recipient's email system.

Method 2. Zip File Attachments to Combine and Compress Them

Outlook’s automatic resizing feature is very useful, but it won’t work for some types of files. For example, suppose you had a large spreadsheet or other large document you wanted to send by email. The resizing feature wouldn't work. Video files are another type of file that frequently exceed the Outlook email attachment limit, but that can't be resized using the resizing feature.

The answer the answer for these large file types is to compress them using a zip file before you attach them to your Outlook email. A zip file can also combine multiple files into a single file.

Creating the zip file automatically compresses your files, but it isn’t useful for file types that are already compressed. For example, .jpg—a popular image format—is already in a fairly compressed state. So, zipping files of this type won’t reduce the size much.

When the recipient receives the zip file, they simply extract the files from the zip file. Let’s get started. In this example, I’ll show you how to email large files of this type through Outlook email.

Step 1. Create a Zip File

The first thing you need to do to is zip your large files. Go to Windows File Explorer and find the files you want to zip. Use CTRL+Shift to select multiple files. Here’s an example of selected files:

Files selected in Windows File Explorer
Select the files you want to zip up in File Explorer.

In this example, I'm using large video files. Notice that together the selected files are slightly over the 20 MB limit. Right-click on the selected files to bring up a pop-up menu:

Compressing video files in Windows Explorer
You can compress large files through the Windows Zip feature.

Go to Send to > Compressed (zipped) folder. The system automatically creates a zipped file containing all the files you selected:

A compressed zip file
The compressed zip file contains each of the original files.

Notice that the zip file size is smaller than the combined total of the original files. If you want, you can now rename this file 

Step 2. Attach the Zip File to your Outlook Email

Once you’ve created your zip file, you can attach it to an Outlook email message using the steps to send an attached file that I described earlier. When you're ready, click the Send button.

Step 3. Extract the Files from the Zip File

Once your recipient has received the email with an attached zip file, they simply need to extract the files. It’s easy if you know what to do. Here’s an email with an attached zip file:

Email with attached zip file
After you've created a zip file you can attach the compressed file to an Outlook email.

To access the files in a zip file from a received Outlook email, click the down arrow at the right of the file. Select the Save As option:

Accessing zipped files in Outlook
Start by saving the zipped file to your computer.

Save the zip file to the folder on your computer where you want to store it. Next, use Windows File Explorer to navigate to the folder where you’ve stored the zip file. Click on the file to select it. Then right-click to bring up the pop-up menu:

Extract the files from a zip file
After you've saved the zip file, you can extract the files it contains.

Select the Extract All menu option.

Saving the extracted files to a folder
Choose a folder location to store the extracted files.

Choose the location for the extracted files and click the Extract button. The files are extracted to your selected location.

Method 3. Send the File Through a Cloud Service

You can also put a large file in a cloud storage area and then share it. Common cloud storage services include Dropbox, Google Drive, and OneDrive.

OneDrive is Microsoft’s cloud storage area. It’s built into Windows. If you've got a Microsoft account, you can store up to 15 GB on your free OneDrive account. You can find OneDrive in your Windows File Explorer (notice the icon that looks like a cloud):

Finding Microsoft OneDrive in File Explorer
OneDrive is Microsoft's cloud storage area.

Step 1. Copy Your Files to OneDrive

Let’s examine how to share large files using Microsoft OneDrive. In the example above, I’ve already created a few folders, including one called Shared Files. To share the files through OneDrive, I open two instances of File Explorer on my PC. I click on the files I want to share to select them and then drag them into the OneDrive folder:

Drag files into OneDrive
You can drag the selected files into a OneDrive folder.

Step 2. Get the Sharing Link

Once the files are in the folder you want share, right-click on the folder name to bring up a pop-up menu. Select More OneDrive Sharing Options. The OneDrive window opens with the Share ‘Shared Files’ dialog box: 

Getting a sharing link from OneDrive
Insert the copied link into your Outlook email to share the large video files.

You’ll see a variety of ways to share the files in your folder, including through social media. To share the files through Microsoft Outlook, click the Copy button to copy the link shown to the clipboard.

Step 3. Add the Link to an Outlook Message

Open Microsoft Outlook and create a new message. Press CTRL+V to paste the link into your email message:

Outlook Email with shared link
The recipient can click the link to access the shared files.

When you're ready, click the Send button to send your email message. When message is received, the recipient can click the link in the email to access the large files you shared. 


In this tutorial, you've learned how to email large files in Microsoft Outlook. You’ve even learned how to send large video files through Outlook.

If you need to send large files through email, it's important to understand about the MS Outlook file size limit. With the methods you learned in this tutorial, however, you can share an Outlook attachment even if it exceeds the Outlook file size limit. 

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