Email was never designed for big files. Attachments are encoded, which makes them about a third larger, and every server along the way has its own size limit. When a message is too large it bounces, or simply never arrives. This guide explains the limits and shows simpler ways to share large files.
Before you start
- Note the total size of the files you want to send. A 30 MB attachment becomes roughly 40 MB once encoded.
Where the limits are
| Step | Typical limit |
|---|---|
| Roundcube webmail upload | Set by the server; often around 25–50 MB per message |
| Your server's maximum message size | Commonly around 50 MB on cPanel servers |
| Recipient's provider (Gmail, Outlook.com) | About 25 MB received for Gmail; Outlook.com around 20–25 MB |
| Recipient's company mail server | Often 10–20 MB |
The smallest limit on the path wins. In practice, keep emails under 10 MB to be safe for any recipient.
Signs a message was too big
- Roundcube shows an error while uploading, or the file never finishes attaching.
- You receive a bounce such as
552 Message size exceeds fixed maximum message size. See bounce errors explained. - Track Delivery shows a rejection mentioning size.
Better option 1: a download link from your hosting
- Create a folder such as
public_html/sharein File Manager. - Upload the file (or use FileZilla for very large files).
- Send the link, e.g.
https://example.com/share/project-files.zip. - Protect it with a password using Directory Privacy if the content is private, and switch off directory listings (Indexes).
- Delete the file when the recipient has downloaded it, so it does not use your disk space.
Warning: Do not use your hosting as permanent public file storage. Large, frequently downloaded files use bandwidth and disk quota, and files that break the terms of service (pirated media, malware) lead to suspension.
Better option 2: cloud storage or transfer services
- Share from OneDrive, Google Drive or Dropbox with a link and an expiry date.
- Run your own private cloud with Nextcloud via Softaculous.
- Use a file transfer service for one-off very large files.
If you must attach
- Compress files into a ZIP; documents and text shrink a lot (photos and videos barely do).
- Reduce image and PDF sizes before attaching.
- Split very large collections into several messages, each well under the limits.