Email a zip file in Outlook by compressing the folder first, clicking the paperclip icon to attach it, then sending — the process works the same across all Outlook versions.
The process for how to email a zip file in Outlook is straightforward once you know the one prerequisite: compress the folder first. A raw folder can't attach as a single file, but a .zip archive bundles everything into one transferable package. The steps are nearly identical whether you use Outlook for Windows, Mac, the web, or mobile — only the size limits change depending on your account type.
The Reason to Zip a File Before Emailing
Outlook cannot attach an uncompressed folder as one file. Zipping it bundles every subfolder and file into a single .zip archive, shrinks the overall size, and preserves the folder structure and metadata for the recipient. Both Windows and Mac include built-in compression tools, so no extra software is needed.
How to Create a Zip File on Windows and Mac
The compression step takes about two seconds on either platform.
On Windows: Right-click the file or folder in File Explorer, choose Send to > Compressed (zipped) folder. Windows creates a new .zip file with the same name in the same location. You can rename it immediately by pressing F2.
On Mac: Right-click the file or folder in Finder and choose Compress. A .zip archive appears next to the original item. Press Return to rename it if needed. Even a small folder benefits from this step — the main goal is to turn the folder into one attachable file.
How to Attach a Zip File in Outlook
The attachment flow is consistent across all Outlook versions. The key is to look for the paperclip icon in the compose window.
Outlook for Windows (desktop): Open a new message, click the Attach File button (the paperclip) in the Include group on the Insert tab, or use the paperclip below the subject line. Browse to your .zip file, select it, and click Insert. The file appears as an attachment line in the message header.
Outlook for Mac: Open a new message, click the Attach paperclip on the toolbar, choose your .zip file, and click Choose.
Outlook on the web (Outlook.com): Start a new message, click the Attach paperclip at the bottom of the compose window, select the .zip from your computer or OneDrive, and the file attaches automatically.
Outlook Mobile: Tap the Attach paperclip in the compose screen, choose Browse or Files, select the .zip, and send. The size limit follows whatever your underlying account uses.
Outlook Attachment Size Limits by Account Type
The limit that applies to your zip file depends on the type of email account and plan you use, not which version of Outlook you open. The table below covers the most common ceilings.
| Account Type | Default Attachment Limit | Notes |
|---|---|---|
| Outlook.com (free) | 25 MB | Per Microsoft's sending limits page |
| Outlook Desktop (POP3/IMAP) | 20 MB (20480 KB) | Default for Internet email accounts |
| Microsoft 365 Outlook Desktop | 35 MB (default), up to 150 MB (admin) | Tenant policy may override |
| Exchange Accounts | 10 MB (default) | Set by Exchange administrator |
| Microsoft 365 (campus/enterprise) | 150 MB total message size | Includes message body and all attachments |
| Outlook Mobile | Matches underlying account | Follows Outlook.com or Exchange limits |
| Registry Override (Desktop) | Custom value in KB | For Internet email accounts only |
If you are unsure which limit applies, send a small test attachment first and watch for the bounce-back message — Outlook's error note usually includes the specific size ceiling.
What to Do When Your Zip File Exceeds the Size Limit?
Zipping a folder does not always shrink it enough. When the .zip file is still over the limit, you have two practical options.
Upload to OneDrive and share a link. Microsoft recommends this as the primary workaround. Upload the file to OneDrive, right-click it, choose Share, and paste the link into your Outlook message. The recipient clicks the link to download the file — no size limit applies, and you keep control over permissions. This is usually the cleanest solution for large files.
Compress further with a third-party tool. Programs like 7-Zip can create smaller archives or split a large zip into multiple parts, but this adds complexity for the recipient. In most cases, the OneDrive link is simpler and more reliable.
Can You Bypass the Attachment Limit with a Registry Edit?
For Outlook Desktop with an Internet email account (POP3/IMAP), you can raise the attachment limit by editing the Windows Registry. Microsoft documents this method specifically for Internet email accounts that hit the 20 MB ceiling.
Navigate to HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Preferences (use 15.0 for Office 2013). Add a new DWORD value named MaximumAttachmentSize and enter the desired limit in kilobytes. Setting it to 0 removes the limit entirely. Microsoft's documentation on attachment size limits covers the full registry path and the caveats — this edit only affects Outlook Desktop, not server-side limits on Exchange or Outlook.com.
Common Mistakes to Avoid
Even with the right steps, a few pitfalls trip up most people at least once.
| Mistake | Why It Fails | The Fix |
|---|---|---|
| Attaching the folder directly | Outlook cannot send an uncompressed folder | Create a .zip archive first |
| Assuming zip always beats the limit | Some files (videos, large PDFs) compress very little | Check the .zip size before sending; use OneDrive if too large |
| Expecting every recipient to open .zip easily | Corporate filters and some mobile mail apps block .zip files | Confirm with the recipient or share a OneDrive link |
| Double-clicking the zip to open inline in Outlook | Outlook prompts you to save it to disk first | Save the .zip to your computer, then extract it |
Step-by-Step Checklist for Emailing a Zip File in Outlook
Follow this sequence to avoid rejections and confusion on the receiving end.
- Compress the folder — Right-click it on Windows or Mac and choose the built-in compression option.
- Check the size — Right-click the .zip file and select Properties (Windows) or Get Info (Mac) to confirm it is within your account's attachment limit.
- Open a new message in Outlook and click the Attach paperclip icon.
- Select the .zip file and attach it. The file appears as a normal attachment line in the message header.
- Add a short note in the body telling the recipient the file is zipped and what it contains.
- Send the email. If it bounces back with a size error, upload the file to OneDrive and send the link instead.
When the .zip is within the limit and the recipient has a way to extract it, the whole routine takes about thirty seconds once you have done it a couple of times.
References & Sources
- Microsoft Support. “Attachment size exceeds the allowable limit error in Outlook.” Official documentation on attachment limits and the registry override.
- Microsoft Support. “Sending limits in Outlook.com.” Confirms the 25 MB limit for Outlook.com accounts.
- Microsoft Support. “Reduce attachment size to send large files with Outlook.” Describes the OneDrive link workflow and image resizing option.