Outlook's limit depends on which Outlook
25 MB on Outlook.com. 20 MB in the Outlook desktop app for internet accounts, and 10 MB on an Exchange server. Microsoft 365 work mailboxes default to 35 MB, and admins can raise that to 150 MB.
Numbers checked outubro de 2026. Each one links to where it came from.
The limits
- Outlook.com, attachments per emailsupport.microsoft.com, checked outubro de 2026
- 25 MB
- Outlook.com, file shared from OneDrivesupport.microsoft.com, checked outubro de 2026
- 2 GB
- Outlook desktop app, internet accountslearn.microsoft.com, checked outubro de 2026
- 20 MBDefault in Outlook 2013 and later
- Outlook desktop app, Exchange serverlearn.microsoft.com, checked outubro de 2026
- 10 MBDefault
- Microsoft 365 work mailboxlearn.microsoft.com, checked outubro de 2026
- 35 MB to send36 MB to receive by default. Admins can set 1 to 150 MB
- Outlook for iPhone and Androidsupport.microsoft.com, checked outubro de 2026
- 33 MB20 MB for iCloud accounts
- Largest file in OneDrivesupport.microsoft.com, checked outubro de 2026
- 250 GB
What happens when it's too big
The Outlook desktop app stops you with an error: "The file you're attaching is bigger than the server allows. Try putting the file in a shared location and sending a link instead." New Outlook and Outlook.com offer to upload the file to OneDrive instead.
Email also grows on the way out. Microsoft says messages leaving its datacenters pick up a 33% encoding increase, so even a work mailbox set to the 150 MB maximum works out to 112 MB.
Outlook's own way round it
Microsoft's answer is OneDrive: upload the file and send a link instead of an attachment. Outlook.com allows OneDrive files up to 2 GB this way, and OneDrive itself takes files up to 250 GB.
It needs room. A free Microsoft account gets 5 GB of cloud storage, shared by OneDrive, your Outlook.com attachments and the Microsoft 365 apps. Anything bigger means buying more storage or clearing some first.
Or skip the upload
download.fyi skips the upload. Drop the file, paste the link into your Outlook message, and it streams straight from your browser to theirs. It works the same for a 30 MB slide deck as for a 30 GB video, and nothing counts against your OneDrive.
Keep the tab open while they download. If they're in another time zone, a pass keeps the file online for 14 days (up to 100 GB, $5) or 30 days (up to 500 GB, $9), paid once.
Questions
Why does Outlook say 20 MB when Outlook.com says 25 MB?
They're different apps. The Outlook desktop app defaults to 20 MB for internet email accounts; the Outlook.com website allows 25 MB.
Can my IT team raise the limit?
On Microsoft 365, yes. Admins can set anything from 1 MB to 150 MB per message. The default is 35 MB to send and 36 MB to receive.
What's the biggest file I can share from OneDrive in Outlook.com?
2 GB.
Does the recipient need Outlook to open a download.fyi link?
No. Any browser works, and nobody signs up.
Other apps' limits
Sign up. Upload. Wait. Just drop it.
No account and no size cap. Your link is ready the moment you pick a file.
Send a file