Outlook Attachment Size Limits
Attachment, mailbox and sending limits for Outlook.com and Microsoft 365
Last reviewed on June 10, 2026
Outlook.com
Per-file attachment
Microsoft 365
Max (admin-configurable)
Via OneDrive
Cloud attachment link
Outlook Limits by Account Type
| Account Type | Attachment Limit | OneDrive Link | Mailbox Size |
|---|---|---|---|
| Outlook.com (free) | 25 MB | 2 GB | 15 GB |
| Microsoft 365 (personal) | Up to 150 MB | 2 GB | 50 GB |
| Exchange (work/school) | 10 MB default (admin-set) | Varies | 50–100 GB |
| Outlook desktop app | Matches account (up to 150 MB) | 2 GB | Per account |
Work and school (Exchange) limits are set by your administrator and default to 10 MB; they can be raised toward the 150 MB ceiling. The recipient's server limit also applies — the smaller of the two wins.
Ways to Send Files in Outlook
📎 Direct Attachment
Outlook.com: 25 MB
- Attach a file from your device
- 25 MB per file on Outlook.com
- Up to 150 MB on Microsoft 365
- Recipient limit also applies
☁️ OneDrive Cloud Link
Up to 2 GB
- Auto-offered for large files
- Shares a link, not the file
- Recipients always can open it
- Default in newer Outlook
💻 Desktop App
Matches your account
- Same caps as web
- Prompts to upload large files
- Insert as a OneDrive link
- Outlook for Windows & Mac
🗜️ Zip & Compress
Stay under 25 MB
- Combine files into a ZIP
- Compress images and PDFs
- Useful for older servers
- Avoids OneDrive entirely
Outlook Sending & Mailbox Limits
📤 Daily Sending (M365)
- 5,000 recipients per day
- 500 recipients per message
- 1,000 new (non-relationship)/day
- Lower for free accounts
Limits curb spam and abuse
📎 Attachments
- Outlook.com: 25 MB per file
- Microsoft 365: up to 150 MB
- OneDrive link: up to 2 GB
- Exchange default: 10 MB
Recipient's limit also counts
💾 Mailbox Size
- Outlook.com free: 15 GB
- Microsoft 365: 50 GB
- Plus 5 GB–1 TB OneDrive
- Work mailboxes: 50–100 GB
Empty Deleted Items to reclaim space
⚠️ Common Errors
- "Attachment exceeds the limit"
- Switch to a OneDrive link
- Compress or split the file
- Check the recipient's cap
Large files? Use OneDrive
Sending Files Larger Than 25 MB
1. Use a OneDrive Link
The modern default:
- Upload up to 2 GB
- Outlook attaches a share link
- Recipients never hit a size cap
- You can revoke access later
2. Compress the File
Squeeze under the cap:
- Zip documents and folders
- Reduce image resolution
- Compress PDFs
- Shrink or trim video
3. Raise the Limit (M365)
For work accounts:
- Admins can raise toward 150 MB
- Set in the Exchange admin center
- Recipient limit still applies
- Not available on Outlook.com
4. Split Into Parts
When cloud isn't an option:
- Split archives with 7-Zip/WinRAR
- Send parts across emails
- Recipient recombines them
- Keep each part under the cap
Frequently Asked Questions
What is the Outlook.com attachment size limit?
Outlook.com allows attachments up to 25 MB per file. For anything larger, Outlook offers to upload the file to OneDrive and insert a share link instead, supporting files up to 2 GB.
Is the Outlook limit 20 MB, 25 MB or 150 MB?
It depends on the account. Outlook.com is 25 MB per file. Microsoft 365 (Exchange) mailboxes can be configured by an admin up to 150 MB, though they often default lower (around 10 MB). The recipient's mail server limit also applies, so the smaller limit wins.
How do I send files larger than 25 MB in Outlook?
Use a OneDrive cloud attachment. Outlook automatically offers this for large files and shares a link rather than the file itself, supporting up to 2 GB. Alternatively, compress or zip the file to fit under 25 MB.
What is the OneDrive attachment limit in Outlook?
When you attach a file via OneDrive in Outlook, the limit is 2 GB. The file is uploaded to OneDrive and a share link is added to the email, so the recipient downloads it from the cloud.
How many emails can I send per day from Outlook?
Microsoft 365 subscribers can send to up to 5,000 recipients per day, with a maximum of 500 recipients per message and 1,000 new (non-relationship) recipients per day. Free accounts have lower limits, and Microsoft may throttle unusual sending activity.