Files too big for email: what happens, and better ways to send them

When a file is too big to attach, put a link in the email instead of the file. Gmail and Outlook will do this for you by uploading the file to Google Drive or OneDrive, which is the easiest route if you have free cloud space. Apple Mail can do the same with Mail Drop for files up to 5 GB. For anything larger, or if you do not want the file in your own cloud storage, use a transfer service or a direct transfer link and paste that into your message. Zipping helps only for files that are not already compressed. Below is what actually happens at the limit, why files a bit under the limit still bounce, and the options ranked.

The limits in one paragraph

Personal Gmail accounts allow 25 MB of attachments per message. Microsoft's help pages put Outlook.com at 20 to 25 MB depending on the article, and say that a default Exchange business mailbox allows 10 MB. Work and school accounts are often set differently by the administrator. The full provider-by-provider table lives in our guide to email attachment size limits; this page focuses on what to do once you hit them.

What your email app does when the file is too big

Gmail

In Gmail, if your attachments exceed the limit, Gmail removes the attachment and adds a Google Drive link to the message instead. The file is uploaded to your Drive and counts against your Google storage, which is 15 GB free and shared with Gmail and Google Photos. Before sending, Gmail checks whether recipients can open the file. If you leave the link restricted to the people in the email, anyone without a Google account (or using a non-Google address) cannot see it, and Gmail prompts you to change the sharing setting. Choosing "Anyone with the link" avoids that problem, at the cost of letting anyone who obtains the link open the file.

Outlook.com and Outlook

Outlook does not silently convert. You attach the file, choose OneDrive if it is already there or Upload and share if it is not, and send a share link. Microsoft's help page says linked OneDrive files do not count toward the email size limit, but sets a 2 GB limit for files linked this way. Free OneDrive storage is 5 GB, so a few large shares fill it quickly. In some Outlook versions you simply see an error when the attachment is too big, and the OneDrive route is the fix Microsoft recommends.

Apple Mail (Mail Drop)

Apple Mail on Mac, iPhone and iPad can offer Mail Drop when an attachment is too large. The file is uploaded to iCloud and the recipient gets a download link. Apple's limits: up to 5 GB per message, links expire after 30 days, and a total of 1 TB of Mail Drop storage at a time. Mail Drop attachments do not count toward your iCloud storage, which makes it the most generous built-in option for Apple users.

Everything else

Many other providers and older desktop clients simply refuse to send, or send the message and then receive a bounce from the recipient's server. That bounce can arrive minutes later with a technical-looking "message size exceeds fixed maximum" style error. The message did not go through, even though it left your outbox.

The hidden overhead: why a 20 MB file is really about 27 MB

Email was designed for text. To carry binary files, mail software encodes attachments as Base64, defined in the MIME standard (RFC 2045). Base64 turns every 3 bytes of input into 4 text characters, and lines are broken at no more than 76 characters. The result is roughly 33 percent larger than the original, plus a little for the line breaks.

Providers do not all count size the same way, and the message body, signature images and headers add to the total. The working rule: if the attachments add up to more than about three quarters of the stated limit, expect trouble, and assume the recipient's server may be stricter than yours.

Better ways to send it, ranked

Ranked for the most common case: one person, one or a few files, sent from a typical personal account.

1. Your email app's built-in cloud link. Gmail with Drive, Outlook with OneDrive, Apple Mail with Mail Drop. It happens inside the email you are already writing, the recipient sees a familiar link, and nothing new needs installing. Watch out for sharing permissions (Gmail) and your free storage quota (Drive and OneDrive). Best for most files up to a few gigabytes.
2. Compress first, if the file is compressible. Zipping a folder of Word documents, spreadsheets, CSV exports or uncompressed TIFF images can bring it under the limit and keep it as a plain attachment. It does almost nothing for JPEGs, MP4 video, MP3 audio or most PDFs. Our guide on how to zip files covers Windows, macOS, iPhone and Android.
3. A transfer service link. Upload to a service and paste its link into the email. At the time of writing, TransferNow offers 5 GB with no registration for 7 days, and SwissTransfer offers 50 GB with a one-time email check and expiry you choose up to 30 days. These keep big files out of your own cloud storage. The downside is that the link expires, so the recipient must download in time. See free ways to send large files for the full comparison.
4. A direct transfer link. Tools like TransferFiles.net give you a link or short code that streams the file straight from your browser to theirs, with no account and no size limit set by the tool. The file is not uploaded to a server. This suits files too large for the options above, but the timing is different from email: the recipient has to open the link while your page is still open, so it works best when you can message them to say "open this now", not as an attachment they read tomorrow.
5. Splitting into several emails. Archive tools such as 7-Zip can create split volumes that each fit under the limit. It works, but the recipient must collect every part and rejoin them, and one missing email breaks the set. Use it only when links are not allowed.
6. Reducing the file. Lowering image resolution, exporting a PDF with compressed images, or re-encoding a video makes the file genuinely smaller. Fine when the recipient does not need full quality. Outlook on Windows can resize large images automatically when sending; for video, see our guide on sending large video files.

Writing the email that carries the link

Swapping an attachment for a link changes how the recipient experiences your message. A few habits make it smooth and safe:

• Say what the link is. Name the file, its size and the service: "Contract scans, 340 MB, via Google Drive." Unexplained download links look exactly like phishing, and careful recipients will ignore them.
• Give the deadline. If the link expires, say when. "Available until Friday" prevents a missed download.
• Check the permissions yourself. Open the link in a private browser window where you are not signed in. If you see a "request access" page, so will they.
• Do not send sensitive files to "anyone with the link" casually. Links get forwarded. For confidential material, restrict access to named people, add a password where the service offers it, or use an end-to-end encrypted or direct method.
• Tidy up afterwards. Files uploaded through Gmail and Outlook stay in your Drive or OneDrive using your quota until you delete them.

When email is the wrong tool altogether

If you regularly exchange large files with the same people, a shared cloud folder beats repeated links. If you are sending to a client who expects a polished delivery page and download tracking, a professional transfer service fits better; our guide to sending large files to clients covers that. And if both of you are online right now, a direct transfer skips the upload-then-download round trip entirely.

Sources

• Gmail Help: attachment size limits
• Gmail Help: insert files using Google Drive
• Microsoft Support: attachment size limits in Outlook
• Microsoft Support: unable to attach files in Outlook.com
• Microsoft: compare OneDrive plans
• Apple Support: Mail Drop limits
• RFC 2045, section 6.8: Base64 content-transfer-encoding
• TransferNow
• Infomaniak: SwissTransfer