Email attachment too large? What to do instead

Friday, 16:52. You attach the scanned contract, press send, and an answer arrives faster than any client has ever replied: 552 message size exceeds fixed maximum. The file said 19 MB. The limit is 25. Your client needs the contract today, and the mail server has other plans.

Email was built for text, so every attachment is turned into text before it travels. The Base64 encoding (opens in a new tab) behind this makes four characters out of every three bytes and adds a line break every 76 characters. The attachment grows by roughly a third on the way, and your 19 MB contract reaches the server as a message of about 26 MB.

Several limits apply to that message, and the lowest one wins: what your provider lets you send, what the recipient’s server accepts and, quite often, a limit your own IT has set. A server that refuses an oversized message answers with code 552, as defined in the SMTP size extension (opens in a new tab), which is why that number turns up in so many bounces. Sometimes the email leaves your outbox without complaint and is turned away only at the other end.

There is no official maximum, but the large mail services sit close together. Free accounts usually stop at 20 or 25 MB per message, all attachments included. Paid and business accounts often allow more, up to whatever the provider or the administrator has set, but a 100 MB message still won’t get far if the recipient has a free account. Since you rarely know what the other side accepts, I treat 20 MB as the ceiling for the whole message, which leaves roughly 14 MB for the files themselves.

Some mail services now go a step further. When a file is too large, they upload it to their own cloud storage and put a download link in the email instead, sometimes without asking. The message goes through, but the file now sits in the provider’s cloud, under whatever sharing settings that link received, and some of these links quietly expire after a few weeks. Worth knowing before a client’s payroll travels that way.

If the file is only slightly too large and nothing in it is confidential, shrinking it is the fastest route. Find out what makes it heavy first. It is almost never the text.

1. 1

   Shrink the PDF.

   Most PDF programs can reduce the file size or optimise it for screens. A scanned letter rarely needs full resolution in colour; greyscale at a moderate resolution reads just as well.

2. 2

   Resize the photos.

   A copy sized for a screen is a small fraction of the original. Keep the originals for the moment quality matters.

3. 3

   Zip what compresses.

   Text files, CSV exports and uncompressed images shrink well in a ZIP. Photos, PDFs and current Office files barely do, because they are compressed already; the ZIP just bundles them.

4. 4

   Split as a last resort.

   Five emails titled “part 3 of 5” are a puzzle for your client and five more copies in five more mailboxes.

Once a file won’t fit, it has to live somewhere else for a while. Every option below solves the size problem. They differ in who can open the file, and for how long.

None of these is wrong in itself. A transfer link is perfectly fine for the new company video. Your client’s bank statements are a different matter, and plain email is no better for them: it is encrypted at best between each pair of mail servers, as the standard itself points out (opens in a new tab), so every server along the way handles the message in readable form.

• Can anyone with the link open it, or only people who sign in? Emails get forwarded, and an “anyone with the link” setting travels with them.
• When does access end, and can you end it earlier yourself?
• Can the service read the file, and in which country is it stored?
• If the link has a password, send it another way, by phone or text message.
• Warn your client. A download page from a service they have never heard of looks a lot like phishing, and careful clients are right to hesitate.

In Encloq, a large file is simply another attachment in the conversation with your client, up to 250 GiB per file within your plan’s storage. It is encrypted on your device before upload, so Encloq stores and delivers it without being able to read it. Uploads can be paused, resumed and retried, which helps when the train enters a tunnel at 87 percent. Your client can open a large PDF without downloading all of it first, and supported RAW photos open as a developed preview.

Clients join through a guest invitation and sign in with a passkey. With Encloq Pro you can cover the storage of the conversations you start, so a large delivery doesn’t eat into your client’s own plan.