How To Attach Large Files In Outlook : Using Attachment Size Limits

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Sending files larger than 20MB through Outlook often fails because of server size limits. Many people search for how to attach large files in outlook and hit a wall when their email bounces back. This guide walks you through every reliable method, from built-in tools to third-party services, so you can share big attachments without frustration.

Outlook has a default attachment limit of 20MB for most accounts. If you try to attach a 25MB video or a large presentation, you will get an error message. The good news is that there are several ways to get around this restriction. You do not need to compress your files into tiny pieces or switch email providers.

In this article, you will learn step-by-step methods for sending large files through Outlook. We cover OneDrive integration, file compression, cloud storage links, and even IT admin settings. By the end, you will know exactly what to do when your attachment is too big.

How To Attach Large Files In Outlook

Let’s start with the most common and easiest method. If you have a Microsoft 365 subscription, Outlook integrates directly with OneDrive. This feature lets you upload your large file to the cloud and send a download link instead of the file itself. The recipient sees the attachment as a normal file, but it does not count against email size limits.

Using OneDrive To Attach Large Files

OneDrive is built into Outlook for Microsoft 365 users. Here is how to use it:

  1. Open a new email in Outlook.
  2. Click the Attach File button in the ribbon.
  3. Select your large file from your computer.
  4. If the file is larger than 20MB, Outlook will ask if you want to upload it to OneDrive and share a link. Click Upload and Share.
  5. Outlook uploads the file to your OneDrive and inserts a link in the email body.
  6. You can adjust permissions by clicking the link and choosing Manage Access.

This method works for files up to 2GB if you have enough OneDrive storage. The recipient does not need a Microsoft account to download the file, but they may need to verify their identity if you set permissions.

Setting Permissions For OneDrive Links

When you share a OneDrive link, you control who can view or edit the file. Click the link in your email draft, then select Manage Access. You can choose:

  • Anyone with the link – No sign-in required, but less secure.
  • People in your organization – Only internal users.
  • Specific people – You enter email addresses manually.

For sensitive files, use the Specific people option. This prevents unauthorized access if the email is forwarded.

Compressing Files Before Attaching

If you prefer to send the file directly without cloud storage, compression can help. Zipping a file reduces its size, sometimes enough to fit under the 20MB limit. Here is how to compress files on Windows and Mac:

On Windows

  1. Right-click the file or folder you want to send.
  2. Select Send to > Compressed (zipped) folder.
  3. A new .zip file appears in the same location.
  4. Attach this .zip file to your Outlook email.

On Mac

  1. Control-click the file.
  2. Choose Compress from the menu.
  3. A .zip archive is created.
  4. Attach it to your email.

Compression works best for text-heavy files like Word documents or spreadsheets. Images and videos may not shrink much because they are already compressed. If your file is still too large after zipping, move to the next method.

Using Third-Party File Sharing Services

When OneDrive is not an option, third-party services are a reliable backup. These tools let you upload your file and generate a shareable link. You paste the link into your Outlook email. Most services offer free tiers with file size limits between 2GB and 5GB.

Popular Services For Large File Sharing

  • WeTransfer – Free for files up to 2GB. No account needed.
  • Dropbox – Free tier offers 2GB storage. You can share links from your account.
  • Google Drive – Free 15GB storage. Works well with Gmail but also with Outlook.
  • Send Anywhere – Free for files up to 10GB. Direct transfer without storage.

Step-By-Step: Using WeTransfer With Outlook

  1. Go to wetransfer.com.
  2. Click Add your files and select your large file.
  3. Enter your email address and the recipient’s email.
  4. Write a short message if needed.
  5. Click Transfer.
  6. WeTransfer sends a download link to the recipient.
  7. Copy the link from the confirmation page and paste it into your Outlook email.

This method avoids Outlook’s size limit entirely because you are not attaching the file. The recipient clicks the link to download.

Splitting Large Files Into Smaller Parts

If you cannot use cloud services or compression, splitting the file into smaller chunks is a workaround. This method is old-school but still effective. You use a file splitter tool to break a large file into several pieces, each under 20MB. Then you attach each piece to separate emails.

Using 7-Zip To Split Files

  1. Download and install 7-Zip (free).
  2. Right-click your large file.
  3. Select 7-Zip > Add to archive.
  4. In the window, set Split to volumes, bytes to 20M (for 20MB parts).
  5. Click OK.
  6. 7-Zip creates multiple files with names like file.7z.001, file.7z.002, etc.
  7. Attach each part to a separate Outlook email.

Tell the recipient to use 7-Zip to combine the parts. They select the first part and extract, and the tool reassembles the original file. This method is clunky but works for any file type.

Adjusting Outlook’s Attachment Size Limit

If you are an IT administrator or have access to Exchange Server settings, you can increase the attachment size limit. This change affects all users in your organization. Be aware that larger attachments consume more server resources and may slow down email delivery.

For Exchange Online (Microsoft 365)

  1. Go to the Microsoft 365 admin center.
  2. Navigate to Exchange admin center.
  3. Click Mail flow > Receive connectors.
  4. Edit the default connector and increase the Maximum message size value.
  5. Save changes.

The maximum allowed size is 150MB for Exchange Online. For on-premises Exchange Server, you can set it higher, but Outlook desktop client may still have its own limit.

For Outlook Desktop (Registry Edit)

Warning: Editing the registry can cause issues. Back up your registry first.

  1. Press Windows + R, type regedit, and press Enter.
  2. Navigate to HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Preferences.
  3. Create a new DWORD (32-bit) value named MaximumAttachmentSize.
  4. Set the value in kilobytes (e.g., 51200 for 50MB).
  5. Restart Outlook.

This registry change only affects the desktop app, not web or mobile versions.

Using Outlook Web App (OWA) For Large Attachments

Outlook on the web (OWA) has a slightly different approach. It also uses OneDrive for files over 20MB, but the interface is simpler. Here is how to attach large files in OWA:

  1. Log in to outlook.office.com.
  2. Click New message.
  3. Click the Attach icon (paperclip).
  4. Select Browse this computer and choose your file.
  5. If the file is large, OWA automatically offers to upload to OneDrive.
  6. Click Upload and share as OneDrive link.
  7. The link appears in the email.

OWA does not have a registry setting, so the OneDrive method is your only option for files over 20MB.

Best Practices For Sending Large Files

No matter which method you choose, follow these tips to avoid problems:

  • Check file size first – Right-click the file and select Properties to see its size.
  • Use descriptive file names – Avoid spaces and special characters to prevent download errors.
  • Set expiration dates – For cloud links, set an expiration date so old links do not linger.
  • Notify the recipient – Send a separate short email telling them to expect a large file link.
  • Test the link – Open the link yourself or send it to a test account to ensure it works.

Common Issues And Fixes

Even with the right method, you might run into problems. Here are frequent issues and how to solve them:

File Still Too Large After Compression

Some files, like high-resolution videos, do not compress well. Use a video compressor tool like HandBrake to reduce the file size before zipping. Alternatively, upload to a video platform like YouTube or Vimeo and share the link.

OneDrive Upload Fails

If your OneDrive upload stops mid-way, check your internet connection. Large files can timeout on slow connections. Try uploading through the OneDrive desktop app instead of the browser. Also, ensure you have enough free storage space.

Recipient Cannot Download The Link

If the recipient sees an error when clicking your OneDrive link, check the permissions. Set the link to Anyone with the link if they are outside your organization. For third-party services, ensure the link has not expired.

Outlook Crashes When Attaching Large Files

This can happen if your Outlook profile is corrupted or if the file is extremely large (over 100MB). Try restarting Outlook, then use the OneDrive method. If the problem persists, repair your Office installation.

Frequently Asked Questions

What Is The Maximum Attachment Size In Outlook?

The default limit is 20MB for most Outlook accounts. For Microsoft 365 business plans, the limit can be increased up to 150MB by an administrator. Personal accounts are stuck at 20MB unless you use OneDrive.

Can I Send A 100MB File Through Outlook?

Yes, but not as a direct attachment. You must use OneDrive, Google Drive, WeTransfer, or another cloud service. Outlook will not allow a 100MB file to be attached directly.

Does Outlook Compress Attachments Automatically?

No, Outlook does not compress attachments. You must compress files manually using a tool like 7-Zip or WinRAR before attaching them.

Why Does My Outlook Say Attachment Size Exceeds The Limit?

This message appears when your file is larger than the server’s maximum message size. The limit is set by your email provider or Exchange administrator. Use OneDrive or a third-party service to bypass it.

How Do I Attach A Folder In Outlook?

Outlook does not support attaching folders directly. You must zip the folder first. Right-click the folder, select Compress (Mac) or Send to > Compressed folder (Windows), then attach the resulting .zip file.

Final Thoughts On Sending Large Files

Knowing how to attach large files in outlook saves you time and frustration. The OneDrive integration is the smoothest option for Microsoft 365 users. For everyone else, compression and third-party services work just as well. Always check file size before sending, and set proper permissions for cloud links.

If you frequently send large files, consider upgrading your OneDrive storage or using a dedicated file transfer service. These tools are designed for big files and offer faster uploads and better tracking. With the methods in this guide, you will never have to worry about Outlook’s size limits again.

Remember, the key is to avoid attaching the file directly if it is over 20MB. Use a link, compress the file, or split it into parts. Each method has its pros and cons, so choose the one that fits your workflow. Now you are ready to send those large presentations, videos, and datasets without any hiccups.