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Quick Answer

Instead of attaching the file directly, upload the large file to your OneDrive, then click Insert > Link in your Outlook email and paste the OneDrive sharing link.

How to Manage Email Attachments and Send Large Files in Outlook ​

Applies to: Outlook (Microsoft 365, Outlook on the web)
Article Type: How-To
Last Updated: 2026-05-17

Summary ​

This article explains how to attach files to emails in Outlook, work around size limits by sharing via OneDrive, handle blocked file types, compress attachments, and manage files you receive.

Prerequisites ​

  • Microsoft 365 account with Outlook access.
  • OneDrive for Business (required for cloud attachment features).
  • For compressed attachments, access to the built-in Windows ZIP tool or a similar utility.

Instructions ​

1. Attach a File to an Email ​

Attach files directly from your computer, recent files, or cloud storage.

From Your Computer ​

  1. Open Outlook and click New Email (or New Message in Outlook on the web).
  2. Click the Attach File button (paperclip icon) in the toolbar.
  3. Select Browse this PC (desktop) or Browse this computer (web).
  4. Navigate to the file, select it, and click Open.
  5. The file appears in the Attached line below the subject.

Drag and Drop ​

  1. Open a new email in Outlook.
  2. Open File Explorer and navigate to the file you want to attach.
  3. Drag the file from File Explorer directly into the body of the email.
  4. The file attaches automatically.

From Recent Files ​

  1. Click the Attach File button (paperclip icon).
  2. Outlook displays a list of your recently used files from OneDrive and your local computer.
  3. Click a file to attach it. If the file is from OneDrive, Outlook may ask whether to attach as a cloud link or a copy.

Verification: The file name, size, and icon appear in the attachment bar of the email.

2. Send Large Files as Cloud Attachments (OneDrive Links) ​

Outlook enforces a 25 MB attachment size limit for email messages. For files larger than this, use a cloud attachment.

  1. Click Attach File (paperclip icon) in a new email.
  2. Select Browse cloud locations > OneDrive, or select a recent file stored in OneDrive.
  3. Choose the file and click Next or Attach.
  4. Outlook attaches the file as a cloud link — indicated by a small cloud icon.
  5. To change permissions, click the dropdown arrow on the attached file and select Change permissions:
    • Anyone with the link can edit — full access, no sign-in required.
    • People in your organization can edit — internal users only.
    • Specific people — only named recipients.
  6. Send the email. Recipients click the link to open the file from OneDrive.

Tip: If you attach a local file that exceeds 25 MB, Outlook automatically prompts you to upload it to OneDrive. Click Upload and share to proceed.

If the file is not yet in OneDrive:

  1. Open File Explorer and copy the file to your OneDrive folder.
  2. Wait for the sync icon to show a green checkmark (✅).
  3. Return to Outlook, click Attach File > Browse cloud locations > OneDrive, and select the file.

Verification: The attachment shows a cloud icon instead of a paperclip, and the file size is not counted against the 25 MB limit.

3. Compress Files Before Attaching (ZIP) ​

For multiple files or files close to the size limit, compressing into a ZIP archive reduces size and keeps everything organized.

  1. Open File Explorer and navigate to the files you want to send.
  2. Select the files (hold Ctrl and click each file, or press Ctrl + A to select all).
  3. Right-click the selection and choose Compress to ZIP file (Windows 11) or Send to > Compressed (zipped) folder (Windows 10).
  4. Name the ZIP file and press Enter.
  5. Attach the ZIP file to your email using Method 1.

Note: See How to Compress and Extract ZIP Files in Windows 11 for detailed instructions.

4. Handle Blocked File Types ​

Outlook blocks certain file types (e.g., .exe, .bat, .cmd, .msi, .js) for security. To send one of these files:

  1. Compress the file into a ZIP archive (Method 3). Outlook does not block .zip files by default.
  2. Upload to OneDrive and share a link (Method 2). Cloud links bypass attachment blocking entirely.
  3. Rename the file extension. Add .txt to the end (e.g., installer.exe to installer.exe.txt). Tell the recipient to remove .txt after downloading.
  4. Use a SharePoint document library for recurring file exchanges with the same team.

Verification: The email sends without an error about blocked attachments.

5. Open and Save Attachments You Receive ​

Handle incoming attachments safely and efficiently.

Preview Before Downloading ​

  1. Open the email containing the attachment.
  2. Click the attachment name. Outlook opens a preview (available for Office documents, PDFs, and images).
  3. To open the full file, click Edit in [App] or Download.

Save Attachments ​

  1. Click the dropdown arrow on the attachment (or right-click it).
  2. Select Save As to save to a specific location, or Save to OneDrive to store it in the cloud.
  3. To save all attachments at once, click Save all attachments (desktop Outlook only).

Verification: The file opens correctly or appears in your OneDrive folder.

6. Manage Attachment Size to Control Mailbox Growth ​

Large attachments are the leading cause of mailbox size warnings.

  1. Send cloud links instead of copies (Method 2) — the file lives in OneDrive rather than consuming mailbox space.
  2. Delete emails with large attachments after saving the files to OneDrive or a shared folder.
  3. Use the Mailbox Cleanup tool: Click File > Tools > Mailbox Cleanup > Find items larger than and set a size (e.g., 5 MB).
  4. Empty Deleted Items regularly — attachments in deleted emails still count toward your mailbox quota.

Verification: Check your mailbox size under File > Office Account. See How to Fix Outlook Not Receiving Emails (Mailbox Over Size Limit) for details.

Troubleshooting ​

TIP

When an attachment fails to send, the most common fix is to upload the file to OneDrive and share it as a cloud link (Method 2). This bypasses both size limits and most blocking rules.

Symptom / ErrorPotential CauseSolution
"The file exceeds the maximum size"File is larger than 25 MBUpload to OneDrive and send as a cloud link (Method 2), or compress first (Method 3).
"Outlook blocked access to the following potentially unsafe attachments"File type is blockedCompress into a ZIP archive (Method 3) or share via OneDrive link (Method 2).
Recipient cannot open the attachmentIncompatible app or corrupt fileRe-send in a different format (e.g., PDF). Confirm the recipient has the required application.
Drag-and-drop inserts an image instead of attachingImage dropped into message bodyDrag the file to the attachment bar, not into the text area. Or use the Attach File button.
Cloud attachment shows "Request access"Permissions too restrictiveClick the attachment dropdown, select Change permissions, and add the recipient.
Mailbox is full — cannot send or receiveAccumulated large attachmentsRun the Mailbox Cleanup tool (Method 6). Delete old emails and empty Deleted Items.