Attachment limits: Gmail, Outlook, and iCloud Mail
Every provider draws a line, and the numbers are close enough that one rule of thumb covers most cases: stay under 20 MB and the message goes through almost anywhere.
| Provider | Limit | What happens above it |
|---|
| Gmail | 25 MB per message | Gmail removes the attachment and inserts a Google Drive link instead |
| Outlook.com | 25 MB for the whole message | Offers to share from OneDrive; links do not count toward the limit |
| iCloud Mail | 20 MB per message | Mail Drop takes over up to 5 GB; recipients have 30 days to download |
Two caveats. The recipient's server has its own limit, and corporate mail systems are often stricter than consumer ones — a message that leaves your outbox can still bounce at the other end. And attachments are encoded for transport, which inflates them by roughly a third on the wire, so a file that looks like it just fits sometimes does not.
Limits checked against Google, Microsoft, and Apple support documentation in August 2026.
Why scanned PDFs get so large
A PDF produced by a word processor stores text as instructions — a few kilobytes for a page of prose. A scanned PDF stores a photograph of each page, at whatever resolution the camera captured. That is the whole difference, and it is why a ten-page scan can outweigh a hundred-page report that was never printed.
Colour makes it worse: a page scanned in full colour carries three channels of data where a black-and-white filter carries far less. This is also why the fix is usually simple — most of those bytes are describing paper texture and lighting, not the words you actually need.
Make the PDF smaller before you send it
- Open the document in ScanLens and tap More → Export.
- Keep the format as PDF and look at the quality options. Each one shows an estimated file size, so you can see the trade before committing to it.
- Step down one level at a time. Going from Maximum to High, or High to Medium, is usually enough for a text document; drop to Low only when the page is simple.
- Export and check the result. Open the new file and read the parts that matter — the small print, the signature, the figures in a table.
- Attach the smaller copy. Your original stays in the library at full resolution, so you can export again at any setting later.
The full guide to reducing PDF size goes deeper into which quality level suits which kind of page.
Send only the pages you need
Often the file is large because it contains more than the recipient asked for — a whole scanned booklet when they wanted the two pages with the terms on them. Cutting pages is the bluntest and most effective size reduction available, and it usually improves the message too.
Drop what does not belong
Blank backs, duplicate captures, and the cover sheet nobody reads. See delete pages from a PDF.
Split a long document
Send a long file in parts when the recipient needs all of it but the mail server will not take it in one go. See split a PDF.
Send a link instead of an attachment
When the file has to stay whole and stay detailed — a signed contract at full resolution, a scanned portfolio — stop fighting the limit and change the delivery method. Upload the PDF and send a link.
iCloud Drive, Google Drive, Dropbox, and OneDrive all do this, and Gmail and Outlook will even offer it themselves once you cross the limit. On iCloud Mail, Mail Drop handles it invisibly: you attach the file as normal and the recipient gets a download link valid for 30 days. See scanning to cloud storage for getting the file up there in the first place.
One consideration before you do: a link can be forwarded, and depending on how you share it, anyone holding it may be able to open the file. For anything sensitive, password-protect the PDF first, or check the sharing permissions on the folder.
Keep it readable: what you lose when you shrink
Reducing quality is lossy by definition. For a printed letter or a form filled in with a pen, the loss is invisible at reading size. The cases where it bites are specific and worth knowing before you send something that matters:
Small print
Footnotes, terms, and the fine print on a receipt lose their edges first — exactly the text a recipient is most likely to need to read closely.
Signatures and stamps
Thin pen strokes and stamp edges blur, which matters when the document is being checked rather than skimmed.
Diagrams and fine lines
Plans, tables with hairline rules, and technical drawings degrade in ways that are hard to spot on a phone screen and obvious in print.
The check that takes ten seconds
Open the exported file, zoom to the smallest text on the page, and decide whether you would accept it if you were the recipient.
Scan smaller from the start
If you scan documents regularly and keep hitting this, the setting to change is upstream. A black-and-white filter on a text document produces a dramatically smaller file than a full-colour capture of the same page, and it usually looks better too — cleaner background, sharper letters.
Colour earns its size when the document actually depends on it: a receipt with a coloured logo you need to identify, a photograph, a highlighted contract. For everything else, choosing the right filter is the setting that does the most work. Scanning several pages into one file from the outset also helps, since one multi-page document is easier to size-manage than a handful of separate images.
