Outlook Attachment Limit: 20 MB, or 10 MB on Exchange
By Shah Zaib · Published
In short: Outlook limits an email to 20 MB on an internet account such as Outlook.com or Gmail, and to 10 MB by default on an Exchange (business) account. The limit counts the attachment and the email together. Compress PDF shrinks a PDF under it in your browser, and Split PDF cuts a long one into parts.
The figures here come from Microsoft's support page on reducing attachment size in Outlook. Which one applies to you depends on the kind of account you send from, so check that first.
What Microsoft says about email size
| Account | Email size limit |
|---|---|
| Internet email, such as Outlook.com or Gmail | 20 MB |
| Exchange (business email) | 10 MB by default |
| What it counts | The attachment and the email together |
The limits in Microsoft's own words
Each limit above, as Microsoft writes it, with a link to the page.
For internet email accounts such as Outlook.com or Gmail, the email size limit is 20 megabytes (MB).
Microsoft: Reduce attachment size to send large files with OutlookFor Exchange accounts (business email), the default email size limit is 10 MB.
Microsoft: Reduce attachment size to send large files with OutlookThis limit includes both the size of the attachment and the size of the email.
Microsoft: Reduce attachment size to send large files with Outlook
How to get a PDF under the limit
- Check the file size. On Windows, right-click the file and choose Properties; on a Mac, choose Get Info. Under your limit, with a little room for the email itself? Attach it as it is.
- Over it? Open Compress PDF, keep Smaller, tick Target max PDF size and type 19,000 KB for an internet account or 9,000 KB for an Exchange account. That leaves room for the email under 20 MB or 10 MB.
- Drop the PDF and click Compress PDF. The new size shows when it is done. Download the file and attach that one.
- Still too big, or the text went soft? Take the PDF apart with Split PDF and send the parts in separate emails.
Pick Smaller for scans and phone photos, where most of the saving is. It makes each page a picture, so the text cannot be selected afterwards. For a PDF the recipient has to copy from, use Keep text: it keeps the text and saves less.
Other ways Microsoft suggests
Compressing is one of them. Microsoft also lists sharing a link to a file saved in a cloud service such as OneDrive, which sends no attachment at all, so the recipient needs access to that link.
There are a few ways to work around this size limit, including using a file sharing service or compressing the file.
Microsoft: Reduce attachment size to send large files with Outlook
Frequently asked questions
What is the Outlook attachment size limit?
20 MB for internet email accounts such as Outlook.com or Gmail, and 10 MB by default for Exchange accounts. The limit includes the size of the attachment and the size of the email.
Sources: Microsoft, Reduce attachment size to send large files with Outlook; Microsoft, Reduce attachment size to send large files with Outlook; Microsoft, Reduce attachment size to send large files with Outlook
Is the Outlook limit for the file or the whole email?
For both together. Microsoft says the limit includes both the size of the attachment and the size of the email, so a PDF just under the limit can still be refused.
Sources: Microsoft, Reduce attachment size to send large files with Outlook
How do I compress a PDF for Outlook?
Open Compress PDF, keep Smaller, tick Target max PDF size and type 19,000 KB for an internet account or 9,000 KB for Exchange. Drop the PDF and click Compress PDF. The file never leaves your browser.
Sources: Microsoft, Reduce attachment size to send large files with Outlook; Microsoft, Reduce attachment size to send large files with Outlook
Why is my Outlook limit 10 MB and not 20 MB?
You are probably sending from an Exchange account, the business kind, where the default limit is 10 MB. Internet accounts such as Outlook.com or Gmail get 20 MB.
Sources: Microsoft, Reduce attachment size to send large files with Outlook; Microsoft, Reduce attachment size to send large files with Outlook
What can I do if the file is still too big?
Microsoft says to use a file sharing service or compress the file. You can also take the PDF apart with Split PDF and send the parts in separate emails.
Sources: Microsoft, Reduce attachment size to send large files with Outlook
Checked against Microsoft's page on reducing attachment size in Outlook on 25 October 2026. Limits can change, so read the page before you send something large.