Email attachment size limits by provider

Between 20 MB and 25 MB on personal email services, and around 35 MB on Microsoft 365 business mailboxes. That limit covers the whole message, not each file, and because attachments are encoded on the way out, a file just under the published figure can still be refused. The table below gives the exact figure for each service, the official page it comes from, and the date we checked it.

Attachment limits by provider

These limits change from time to time. If a delivery matters, open the provider's page before you rely on the figure.

Four details that change the number in the table

The limit is per message, not per file. Yahoo puts it most plainly: the sum of all files attached to one message must not exceed 25 MB. Four 7 MB photos break the limit even though none of them reaches it on its own.

Encoding makes the message bigger. An attachment does not travel as the raw file. It is encoded as text, and that adds weight. Microsoft documents an increase of about 33% for messages that leave its data centres. In practice, with a 25 MB limit the safe ceiling is around 18 to 19 MB of files.

The recipient's limit counts, not only yours. The message passes through two servers and the stricter one decides. A 24 MB file leaves Gmail and is then refused by an iCloud Mail inbox that stops at 20 MB. If you do not know what the recipient uses, plan for the smallest figure in the table.

On Microsoft 365 the limit is a setting. 35 MB is the default, and Microsoft's documentation says administrators can set their own limit anywhere between 1 MB and 150 MB. Inside an organisation, the real limit is known by the administrator, not by the table above.

What each service does when you go over

None of them simply loses your message, but most of them switch method and move the file into their own storage:

• Gmail removes the attachment and adds a Google Drive link instead, which then counts against your Google storage.
• Outlook.com lets you share the file from OneDrive instead, where its page puts the attachment limit at 2 GB.
• iCloud Mail offers Mail Drop, which takes messages up to 5 GB, and Apple's Mail Drop page gives recipients 30 days to download (checked on 29 September 2026).

All three are sensible when you already live in that ecosystem and so does the recipient. When you do not, you are asking the other person to deal with an account or an unfamiliar screen at exactly the moment they only wanted a file.

When a transfer link is the better answer

A transfer service solves the same problem another way: the file goes neither into the message nor into your permanent storage. You send a link, the recipient opens it in a browser, and the link stops working on the date you chose. Nobody creates an account to download.

Transferify has two ways to send. Instant transfer goes straight between the two browsers, peer-to-peer, and is never stored on our servers. Instant is free up to 5 GB on the free plan; above that, any paid plan unlocks any size. The only condition is that your tab stays open until the download finishes.

A hosted link is encrypted on your device before it is uploaded, and it keeps working after you close your laptop. The free plan includes 50 downloads a month, and the size each plan allows is on the pricing page.

Where to go next

For the practical steps, carry on with the guide on how to send large files by email. If the attachment that will not fit is a set of drawings or a quote, the page for construction and trades covers how those packages travel.

If what you need to send is not just over the limit in the table but tens of gigabytes, the question changes from "which method" to "what does it cost". The guide on sending files of 20 GB and more has the answer, and the overview of how to send large files compares every method side by side.

Send the file as a link instead. The recipient downloads it in the browser, with no account and nothing to install.