How to send large files by email (without hitting attachment limits)

Every mail provider caps attachment size, typically between 20 and 50 MB. The cap is not arbitrary: attachments are encoded for transport, which inflates them by roughly a third, and the message must be accepted by the recipient's server as well as yours. The smaller of the two limits wins — which is why a file that sent fine yesterday bounces today.

Why the limits exist

Mail was designed for text. Base64 encoding a binary file adds about 33% to its size, so a 20 MB file arrives as roughly 27 MB of message. Servers store every copy in every recipient's mailbox, so a 20 MB file sent to ten colleagues consumes 200 MB. Limits keep queues moving and mailboxes usable.

Options that work

Cloud storage links. The standard answer: upload the file, send a link. The message stays small, the recipient downloads at their convenience, and you can revoke access afterwards. Use a link with an expiry date for anything sensitive, and a password where the content warrants it.

Compression. Zipping helps for documents, spreadsheets and text — often dramatically. It does almost nothing for photos, video or PDFs that are already compressed. Compress before you conclude that a file is too large.

Splitting archives. Multi-part archives get around a hard limit but are awkward: the recipient needs every part and a tool that understands the format. Use only as a last resort.

Reducing the file. Export a presentation to PDF, downsample images, or trim a video. Often the fastest fix is simply a smaller file.

Transfer services. Fine for one-off transfers with external parties; check the retention and privacy terms before sending anything confidential.

Choosing for sensitive material

For anything confidential, a link beats an attachment. An attachment is copied into every recipient's mailbox and any forward beyond it, with no way to withdraw it. A link can expire, can be password-protected and can be revoked when the project ends. If the content is genuinely sensitive, protect it at the file level too — see our guide to sending encrypted email.

Practical etiquette

• Tell the recipient what the link contains and when it expires.
• Do not send large attachments to distribution lists — one file, dozens of copies.
• Name files descriptively; final_v3_FINAL.pdf helps nobody.
• Check the recipient's limit before a large send if it matters. When in doubt, link.

Frequently asked questions

What is the usual attachment limit? Commonly 20–50 MB, but the recipient's server may be stricter than yours.

Why did a 20 MB file fail on a 25 MB limit? Encoding overhead. Assume roughly a third is added in transit.

Are cloud links safe? As safe as their settings. Use expiry dates, restrict access where possible, and do not post links publicly.

Can I send a video by email? Rarely a good idea. Upload it and share a link — video files exceed limits almost immediately.

Large files with imail Drive

imail Drive lets you upload files and share them with a public link or a private, code-protected one, and every upload is scanned for malware. Details are on the features page; to try it, create a free account.