Quick answer: a free Outlook.com account can send up to 20 MB of attachments per email. Work and school Microsoft 365 accounts usually allow around 25 MB of attachments, unless your IT team changed it. For anything bigger, share a OneDrive link or upload the file to a transfer service and paste the download link into your email.
Outlook is one of the most common email apps in offices, and its attachment limit is one of the most common reasons a big file does not get through. The confusing part is that there is no single Outlook limit. It depends on which kind of account you have and which Outlook app you use.
Outlook’s limits, by account type
| Account | Attachment limit | Who sets it |
|---|---|---|
| Outlook.com, Hotmail, Live (personal, free) | 20 MB per email | Microsoft, fixed |
| Microsoft 365 work or school account | Around 25 MB of attachments by default | Your IT admin, up to 150 MB |
| Classic Outlook desktop with a Gmail, Yahoo or other IMAP/POP account | 20 MB by default | The Outlook app, plus your email provider |
Limits as of October 2026. For work accounts, Microsoft’s default message size is a little over 30 MB, but attachments grow by about a third when they are encoded, so the usable space for files is closer to 25 MB.
Even if your company raised its limit, the email still has to be accepted by the other side. Gmail and Yahoo Mail stop at 25 MB, so a 40 MB email from a generous Microsoft 365 setup can still bounce.
What Outlook does with big files
When you attach a file that is too big, Outlook offers to upload it to OneDrive and share it as a link. Free Microsoft accounts come with 5 GB of OneDrive storage.
This works well inside a company that already uses OneDrive and SharePoint. It is less smooth for outside recipients: depending on your settings, they may need to sign in with a Microsoft account, request access, or deal with a link that only works for people in your organisation.
How to send large files from Outlook
Option 1: paste a transfer link
This works with every Outlook account and every recipient.
- Upload your files to Nashr, up to 2 GB per transfer, no account needed.
- Choose when the link expires and, if you like, add a password.
- Copy the link and paste it into your Outlook email.
The email stays tiny, so it never bounces, and the recipient downloads the files in a browser without signing in anywhere. You can turn on a download alert to get an email when they do.
Option 2: share from OneDrive
If your colleague is in the same organisation, let Outlook upload the file to OneDrive. Check the sharing option before you send: “People in your organisation” links will not work for outside clients.
Option 3: compress the files
For folders of documents and spreadsheets just over the limit, a ZIP file can save enough space. It will not help much with videos, photos or audio, which are already compressed.
Option 4: ask IT to raise the limit
On a work account, admins can raise the message size limit as high as 150 MB. It is worth asking if your whole team sends big files every day, but it does not solve the problem of recipients whose email providers stop at 20 to 25 MB.
Tip: if your company blocks file-sharing sites, check with IT before using any external service. Nashr links expire automatically and transfer pages are hidden from search engines, which makes them easier to approve.
Fixing “attachment size exceeds the allowable limit”
This error in classic Outlook means the file is over the limit for your account. You can:
- send it as a link instead of an attachment,
- save it as a smaller version (for example, export a PDF with compressed images),
- or remove other attachments from the same email, because the limit counts all files together.
There is a registry setting that changes the limit in classic Outlook, but raising it only helps if your email server and the recipient’s server accept bigger messages too. For most people, a link is faster and more reliable.
Outlook vs Gmail vs Yahoo limits
| Email service | Max attachments per email |
|---|---|
| Outlook.com | 20 MB |
| Microsoft 365 (default) | About 25 MB |
| Gmail | 25 MB |
| Yahoo Mail | 25 MB |
If you also use Gmail, our Gmail attachment size limit guide explains how Google Drive links work there.
Too big for Outlook? Send it with Nashr and paste the link into your email. Free up to 2 GB.
For a full rundown of free options, read how to send large files for free.
Frequently asked questions
What is the maximum attachment size in Outlook?
Outlook.com allows 20 MB per email. Microsoft 365 work accounts usually allow about 25 MB of attachments by default, and admins can raise that.
How do I send a file larger than 20 MB in Outlook?
Upload it to OneDrive or a transfer service like Nashr, then paste the link into your email. The recipient downloads the file from the link.
Can I increase Outlook’s attachment limit?
On a work account, your admin can raise it up to 150 MB. On a personal Outlook.com account you cannot. Either way, the recipient’s email provider may still reject large emails.
Do outside recipients need a Microsoft account to open OneDrive links?
It depends on the sharing setting you choose. Links set to work only for people in your organisation will not open for outside clients.
Is it safe to send work files with a transfer link?
Add a password, set a short expiry and limit the number of downloads. For very sensitive files, use private mode, which encrypts files in your browser before they upload.
