How to send large files in Outlook, whatever your account

What is the Outlook attachment size limit?

There isn’t one Outlook limit but several, because “Outlook” covers a free webmail, desktop apps and Microsoft’s business email. These are the figures Microsoft documents as of October 2026:

If you see “Attachment size exceeds the allowable limit”, you’ve hit one of these caps. Keep in mind that attachments grow by roughly a third when encoded for email, and that the recipient’s server can be stricter than yours: a 30 MB file sent from Microsoft 365 can bounce off a 25 MB inbox.

Your options when a file is too big for Outlook

How to send large files through Outlook with a link

1. 1

   Step 1

   Upload to Transfr

   Open transfr.me in your browser and drop the files or a folder. Up to 100 GB per transfer, no account needed.

2. 2

   Step 2

   Pick Link, then the options

   Choose Link. Set how long it stays up (1, 3, 5 or 7 days free), add a password or a download limit if needed.

3. 3

   Step 3

   Copy the link

   When the upload finishes, click Copy link.

4. 4

   Step 4

   Paste it into your Outlook message

   In Outlook on Windows, Mac, the web or the mobile app, write your email and paste the link. The message stays a few kilobytes, so no limit applies.

5. 5

   Step 5

   Send

   Your recipient clicks, previews and downloads, without creating an account. Send any password by phone or text, not in the same email.

Sending large files outside your organization

At work, the problem is often not your limit but everyone else’s. Exchange Online defaults to 35 MB, but admins can set different limits per mailbox, and partners’ servers may quarantine large messages or strip certain file types. OneDrive links to external people can also be blocked by company policy, or require the recipient to verify their email with a code. A transfer link that anyone can open avoids both, while a password and short expiry keep control. If your company has a list of approved tools, check it first: some IT teams allow specific transfer services and block others.

Regular deliveries to clients? Transfr Pro adds your logo and background to the download page, a custom domain, and Send & Track to see when files were opened. Teams of up to 10 people share the same branding. See file sharing for agencies.

Outlook vs OneDrive vs a transfer link

When you attach a big file in Outlook.com, it offers to upload it to OneDrive and share a link. That works well inside Microsoft 365, where your colleagues already have access. For outside recipients and one-off sends, it has costs: the file takes space in your 5 GB of free OneDrive storage until you delete it, and you have to decide between a public link and one that requires a sign-in. A transfer link lives for the days you choose, then the files are deleted.

How to send a large video or zip in Outlook

• Videos: a minute of 4K phone footage usually weighs well over 25 MB. Send it as a link to keep the original quality; your recipient can play common formats like MP4 in the browser. See send large video files.
• Zip files: zipping does little to media files that are already compressed. Send the folder through Transfr instead; it keeps its structure. See send a large zip file.
• PDFs and scans: a 100-page scanned contract can be 50 MB or more. See send a large PDF.

Secure file transfer from Outlook

For confidential documents, turn on Transfr’s optional end-to-end encryption: files are encrypted in your browser before upload, and the decryption key sits in the part of the link after the “#” and is never stored on our servers. Combine it with a password shared by phone, and a one-download limit. Our secure file transfer guide lists what to check, and law firms will find specific advice for client documents.

Also using Gmail? See send large files with Gmail, or the general guide to emailing large files.