Most personal email accounts cap a message at 20 to 25 MB. Gmail and Yahoo allow 25 MB, Outlook.com and iCloud Mail allow 20 MB, and work accounts are whatever your IT admin set (Microsoft's own default for business Exchange accounts is just 10 MB). The number on the provider's help page isn't quite the size of file you can send, though. Attachments get re-encoded for transport and grow by about a third, so a 20 MB PDF can bounce off a 25 MB limit. Below are the limits, the real file sizes that fit, and what to do when yours is too big.
These are the limits each provider publishes for personal accounts, checked against their help pages in October 2026. The limit is for the whole message, so three 9 MB files count as 27 MB, not three separate 9s.
| Provider | Message limit (personal account) | What happens above it |
|---|---|---|
| Gmail | 25 MB | Gmail swaps the file for a Google Drive link automatically |
| Yahoo Mail | 25 MB total, sending and receiving | The attachment won't upload |
| Outlook.com | 20 MB, including the message text | Outlook offers to share it from OneDrive instead |
| iCloud Mail | 20 MB, sending and receiving | Mail Drop takes files up to 5 GB if it's switched on |
| Proton Mail | 25 MB, up to 100 files | Use a Proton Drive link |
| Microsoft 365 / Exchange (work) | Set by your admin. Microsoft's Outlook help gives 10 MB as the Exchange default; Exchange Online tenants can go up to 150 MB | Usually a bounce message from the server |
| Google Workspace (work or school) | Set by your admin | Same Drive-link behavior as personal Gmail |
The receiving side matters as much as yours. If you send a 24 MB file from Gmail to someone on Outlook.com, you're over their 20 MB ceiling and the message can come back undelivered, even though Gmail let you send it. When you don't know what the other person uses, 10 MB is the safe target. It gets through almost everything, including strict corporate gateways.
Email was built to carry plain text, so binary files like PDFs and photos get converted with an encoding called Base64 before they travel. Base64 turns every 3 bytes into 4 text characters and adds a line break every 76 characters. That makes the attachment about 37% bigger on the wire than it is on your disk.
Providers don't all say whether their limit counts the original file or the encoded message. Mail servers along the way often measure the encoded message, though, and Microsoft has documented that mail leaving Office 365 gets about a 33% encoding increase on top of the file size. Here's what that means in practice if the limit is applied to the encoded message:
| Message limit | Largest file that fits after Base64 encoding | Comfortable target |
|---|---|---|
| 10 MB | about 7.3 MB | 7 MB |
| 20 MB | about 14.6 MB | 14 MB |
| 25 MB | about 18.3 MB | 18 MB |
| 35 MB | about 25.6 MB | 25 MB |
| 50 MB | about 36.5 MB | 35 MB |
The math is simple: divide the limit by 1.368 (that's 4/3 for the encoding times 78/76 for the line breaks). Leave a little room on top for the message body, your signature and any inline images, which all count.
PDFs are the most common oversized attachment, and they're also the easiest to shrink, because the bloat almost always comes from images. A text-only PDF of 50 pages is often under 1 MB. The same document scanned at 300 DPI can be 30 MB or more.
Zipping a PDF doesn't help much. PDFs are already compressed internally, so a ZIP usually saves only a few percent. Zipping is worth it for folders of text files or spreadsheets, not for PDFs or JPGs.
Send a link instead of the file. Every big provider has this built in now, and it's the right answer for anything over 25 MB: video, large photo sets, design files, multi-hundred-page scans.
Links have one big privacy advantage over attachments: you can revoke them. Once an attachment lands in someone's inbox, it's out of your hands for good. A shared link can be switched off once they've downloaded it.
Often, yes. Companies set their own caps, and many sit at 10 to 20 MB to keep mailbox storage and malware scanning under control. Some security gateways also block certain file types outright no matter how small they are, such as .exe, .js or password-protected ZIPs that can't be scanned. If a message to a business address keeps bouncing, read the bounce notice. It usually tells you whether the problem was size ("message size exceeds fixed maximum") or content. When it's size, compressing or sending a link fixes it. When it's a blocked file type, ask the recipient how they'd like to receive it.
25 MB per message for personal Gmail accounts, counting all attachments together. Anything bigger is automatically uploaded to Google Drive and sent as a link. Google Workspace accounts follow whatever limit the administrator sets.
Microsoft's help pages give 20 MB for Outlook.com and other internet accounts, including the message text. For business Exchange accounts the default is 10 MB, but admins can change it, and Exchange Online allows up to 150 MB.
Attachments are Base64-encoded for transport, which makes them about 37% bigger. A 20 MB file becomes roughly 27 MB on the wire, which is over a 25 MB limit if a server counts the encoded size. Keep files under about 18 MB for a 25 MB limit.
Compress it first, which works especially well for scanned PDFs. If it's still too large, split it into parts and send them separately, or upload it to a cloud drive and email a share link.
About 10 MB. That fits under virtually every personal and corporate email limit, even after encoding overhead. For anything bigger, a cloud share link is more reliable.