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Home / Guides / Compress PDF for Outlook

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How to Compress PDF for Outlook and Microsoft 365

Compress PDF for Outlook.com 20MB and Microsoft 365 10MB. Both limits explained with fixes. Browser-based, no upload, no signup, no watermark, instant.

5 min readUpdated 6 days agoNo upload

PPDFWix Team· Reviewed for accuracy

Files never uploaded Runs in your browser No signup No watermark

Compress PDF Free

Live · in browser

Outlook has two different limits: Outlook.com personal accounts allow 20MB, Microsoft 365 corporate accounts are often set to 10MB by IT administrators. Compress your PDF to under 10MB using PDFWix to guarantee delivery to all Outlook recipients. Processing stays in your browser — no upload.

Outlook.com vs Microsoft 365: two different limits

Outlook has two separate products with different attachment limits, and this is the source of most confusion. Outlook.com (the personal web email at outlook.com, hotmail.com, live.com) allows attachments up to 20MB. Microsoft 365 Outlook (the corporate email used in companies) has a limit configured by the company IT administrator — this is typically 10MB, 20MB or 25MB, but defaults to 10MB in most Microsoft 365 tenants.

This means a 15MB PDF attached from your personal Outlook.com may send successfully, but the same file sent to a colleague's corporate Microsoft 365 inbox may be silently rejected.

The safe limit for all Outlook recipients

To guarantee delivery to any Outlook account — personal or corporate — keep attachments under 10MB. This is below the Outlook.com 20MB limit and below the typical corporate 10MB default. For large documents that must remain above 10MB, use OneDrive: upload to OneDrive, right-click, Share, copy link, paste into the email body instead of attaching.

How to compress PDF for Outlook

Open PDFWix Compress PDF — no Outlook account needed, browser-based.
Upload your PDF. It stays in your browser — nothing is sent to PDFWix servers.
Choose Recommended compression for most documents. Check the output size.
If still above 10MB, choose High compression.
Download and attach to your Outlook email.

How to check a company's Outlook attachment limit

There is no visible indicator of an Outlook tenant's maximum attachment size. The only reliable test is to send a test email with the large attachment to yourself or a colleague at the same company. If you receive a bounce-back, the file was rejected. Most corporate IT policies set the limit at 10MB. When in doubt, compress to under 10MB or use OneDrive sharing. See also Gmail attachment limits for comparison.

Use the free PDFWix tool:

Compress PDF Free →

Frequently asked questions

How do I know if my Outlook has a 10MB or 20MB limit?

There is no easy way to check your specific limit without asking your IT administrator. Outlook.com personal accounts are 20MB. Corporate Microsoft 365 accounts depend on company IT policy — the default is 10MB but varies. When uncertain, compress to under 10MB to guarantee delivery.

What happens when I exceed the Outlook attachment limit?

Outlook will show an error message before sending: 'The attachment size exceeds the allowable limit.' You cannot send the email until you remove or reduce the attachment. Compress the PDF first using PDFWix, then re-attach.

Can I send a large PDF from Outlook without compressing it?

Yes — use OneDrive file sharing. Attach the file to OneDrive first, then in Outlook click Insert > Attach File > Browse web locations > OneDrive. Outlook inserts a sharing link. The recipient downloads directly from OneDrive with no attachment size limit.