Limits by provider
Gmail: 25 MB per email (larger files are offered as a Google Drive link). Outlook.com: 20 MB (larger files go via OneDrive). Yahoo Mail: 25 MB. iCloud Mail: 20 MB, or up to 5 GB with Mail Drop. Business mail servers often set their own, sometimes lower, limits. Figures are as published by each provider at the time of writing.
Why a 20 MB file can still fail
Email converts attachments to text using an encoding called base64, which makes them about a third bigger on the way out. A 20 MB file becomes roughly 27 MB in transit, which is over Gmail's limit. As a rule of thumb, treat the real limit as about three quarters of the stated one.
The receiving server matters too. Your provider might accept a 24 MB attachment, but if the recipient's company mail server only allows 10 MB, it will bounce.
What to do when your file is too big
Send a link instead of the file. You can use your email provider's cloud drive, or a transfer service like Skypost, where you get three words to paste into your email. Free files can be up to 200 MB each and the recipient does not need an account. Our large file guide covers all the options.
