Common attachment size limits
- Gmail: 25 MB per email (across all attachments combined)
- Outlook / Microsoft 365: 20 MB by default, though some organizations set it lower
- Yahoo Mail: 25 MB
- Many corporate email systems: often capped much lower, sometimes 10 MB or less
A scanned multi-page document, especially one scanned at high resolution, can easily exceed these limits on its own.
The fastest fix: compress before sending
Running a scanned PDF through a compressor before attaching it is usually enough to solve the problem outright — image-heavy scans often shrink by 60–90% with no visible quality loss on screen, since email attachments are almost always viewed on a monitor or phone rather than printed.
If compression alone isn't enough
- Split the document and send it as two or more smaller emails or attachments.
- Use a cloud link instead — uploading to Google Drive or Dropbox and sharing a link avoids attachment limits entirely, and is often the better choice for files that will stay large no matter what.
- Re-scan at a lower resolution if you're the one creating the scan — 150 DPI is usually plenty for a document that will only be read on screen.
Quick fix
Run your file through the PDFGuy Compress PDF tool before attaching it — it works entirely in your browser and typically takes a few seconds.