Attachment too large: why your email bounces, and how to send the file anyway
Gmail, Outlook, iCloud, Orange: the real limits, the error messages, and the method that works every time.
The short answer. No mail service accepts an attachment over 25 MB, and the real limit is lower still: the message encodes the file in a format that inflates it by about a third. A 19 MB file weighs 25 once it is inside the email, which is why it bounces.
The only method that works every time: do not put the file in the email. Send a link instead.
The real limits, service by service
The right-hand column is the one that matters: it is the size your file can be on disk for the message to get through.
| Mail service | Advertised limit | File size actually accepted |
|---|---|---|
| Gmail | 25 MB | ≈ 18 MB |
| Outlook (desktop, POP/IMAP account) | 20 MB | ≈ 15 MB |
| Outlook / Exchange (business) | 10 MB by default | ≈ 7 MB |
| iCloud Mail | 20 MB | ≈ 15 MB |
| Orange Mail | 25 MB | ≈ 18 MB |
So there is no safe threshold below 25 MB. Between 7 and 18 MB lies a grey zone where the message reaches some recipients and not others.
Why a file smaller than the limit gets refused
This is the point the official help pages skip over, and it is almost always the explanation. An email can only carry text. A file — video, photo, PDF, archive — therefore has to be converted into printable characters before it leaves: that is base64 encoding, which writes three bytes as four characters. The file grows by about 33 % in transit.
In other words: to fit inside a 25 MB limit, your file must not exceed about 18 MB on disk. For a 20 MB limit, count on 15 MB. And that limit applies to the whole message — the text, your signature, the inline images and every attachment added together, not just the file you have dragged in.
One last factor, this one invisible: the lower of the two limits decides, yours when sending and the recipient's when receiving. A corporate server often caps at 10 MB. Your message leaves, appears to be sent, and then a non-delivery report comes back an hour later.
The error messages, and what they mean
Outlook refuses before sending, with this sentence:
The file you're attaching is bigger than the server allows. Try putting the file in a shared location and sending a link instead.
Gmail does not refuse: it silently removes the attachment and replaces it with a Google Drive link, which solves one problem and creates three others — see the article on Gmail.
iCloud Mail offers to switch to Mail Drop. Orange, SFR, Free often accept the message, then send back a non-delivery report later.
An immediate refusal is good news: you see it. The bad case is the message that seems to have left and comes back as a failure two hours later, once you have moved on to something else.
Shrinking the file: what works, what does not
- Zipping a video, a photo or a PDF: pointless. Those formats are already compressed, the gain is measured in percent.
- Zipping a folder of many small files: useful, but to group them, not to make them lighter.
- Re-encoding a video: an hour of computation, a permanent loss of quality, and a result still too heavy nine times out of ten.
- Splitting across several emails: multi-part archives (
.zip.001) assume the recipient knows how to reassemble them, and many mail services block those extensions.
Sending a link: the options built into your mail service
Each mail service offers its own storage: Google Drive for Gmail, OneDrive for Outlook, Mail Drop for iCloud, Orange Cloud for Orange. They share three flaws.
- The file stays in your space after sending, and eats into your quota there.
- Sharing often assumes the recipient has an account on the same side, or that they request an access permission you will have to approve.
- The ceilings stay modest as soon as video is involved: 5 GB for Mail Drop, and Google's free 15 GB quota is shared with your entire mailbox.
toobigtoshare: the link, without the rest
This is exactly the problem this service solves, and nothing else. You drop the file — up to 2 TB, a thousand times the Mail Drop limit —, you get a link, you paste it into your email. No account to create, neither on your side nor on the side of the person receiving: they click, they download.
$5.49 per send, no subscription. The file is permanently erased after 3 days: nothing lingers in a storage space you would have forgotten about.
Frequently asked questions
What is the maximum size of an email attachment?
25 MB at best (Gmail, Orange, Yahoo), 20 MB on Outlook and iCloud, 10 MB by default on a corporate Exchange account. Since encoding inflates the file by about 33 %, the file itself must not exceed 18 MB for a 25 MB limit.
Why is my 20 MB file refused when the limit is 25 MB?
Because the attachment is base64-encoded before sending, which makes it a third heavier: 20 MB on disk becomes roughly 27 MB inside the message. On top of that come the text, the signature and the inline images, which count towards the same limit.
How do I email a 1 GB file?
You do not put it in the email: no mail service will accept it. You upload the file to a transfer service and paste the resulting link into the message. toobigtoshare accepts up to 2 TB with no account to create.
Does zipping the file solve the problem?
Rarely. A video, a JPEG photo or a PDF is already compressed: a ZIP saves only a few percent. ZIP is only useful for grouping many small files into a single send.
Got a file of several gigabytes to send?
toobigtoshare carries up to 2 TB. No account to create, neither for you nor for the person receiving: you get a link, you paste it into your email. $5.49 per send, file deleted after 3 days.