Quick answer: Outlook.com's limit is 20 to 25 MB per email. Microsoft's help pages give 20 MB per message and a 25 MB attachment limit for Outlook.com. Larger files can be shared as a OneDrive link. For anything bigger, send a download link: Share Large Video Files takes up to 20 GB per transfer, free and without an account.
The Outlook limit
| Account | Limit | Details | Checked |
|---|---|---|---|
| Outlook.com | 20 to 25 MB per email | Microsoft's help pages give 20 MB per message and a 25 MB attachment limit for Outlook.com. Larger files can be shared as a OneDrive link. Source | Sep 2026 |
| Outlook / Exchange Online (work accounts) | 35 MB to send, 36 MB to receive (default) | Default for Microsoft 365 mailboxes; admins can set anything from 1 MB to 150 MB. Encoding adds about a third to attachments. Source | Sep 2026 |
Email encodes attachments before sending, which makes them about a third larger. A file just under the limit can still be refused.
What happens when a file is too big
Your email app refuses to send the message, or the attachment is swapped for a cloud-storage link. The recipient's provider can also reject a message that your provider accepted, because its limit may be lower.
How to send a bigger file with Outlook
Send a download link instead of the file. The link is short text, so it fits in any email:
- Open Share Large Video Files in any browser and choose Get a link (or Send by email).
- Drop the file on the upload box, or pick a whole folder. Up to 20 GB and 1000 files per transfer.
- Optional: add a password, a download limit or an expiry under More options.
- Copy the link (or show the QR code) and send it by chat or email. The recipient downloads the original file, byte for byte.
Compared with other email providers
| App | Limit |
|---|---|
| Gmail | 25 MB per email |
| Yahoo Mail | 25 MB per email |
| iCloud Mail | 20 MB per email (5 GB with Mail Drop) |
| Proton Mail | 25 MB per email |
| Share Large Video Files | 20 GB per transfer, free |
Frequently asked questions
What is the Outlook attachment size limit?
Outlook.com: 20 to 25 MB per email. Microsoft's help pages give 20 MB per message and a 25 MB attachment limit for Outlook.com. Larger files can be shared as a OneDrive link.
How do I send a file larger than the Outlook limit?
Upload it to Share Large Video Files (up to 20 GB, free, no account) and paste the download link into Outlook. The recipient gets the original file.
When was this limit checked?
On September 29, 2026, against Outlook's own help pages (linked in the table). Services change their limits, so follow the source link if your file is close to it.
Which apps accept bigger files than Outlook?
Of the email and chat apps we track: Microsoft Teams (chat) (250 GB per file), Telegram Premium (4 GB per file), WhatsApp (document) (2 GB per file), Telegram (2 GB per file), Slack (1 GB per file). Cloud drives and transfer services go much higher; Share Large Video Files takes up to 20 GB per transfer, free.
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