Written by Jennifer Walsh. Reviewed for technical accuracy by Shubham Dixit, Independent Expert in Email Forensics and Data File Conversion.
Shubham is an independent external reviewer and not an employee of PCDOTS.
Quick answer. Roundcube is a webmail viewer sitting over an IMAP server, not a place you drop a file, so it has no real import for a whole MBOX. To import MBOX to Roundcube you upload the mail into the IMAP mailbox, add the account to Thunderbird and drag the messages up, or use a tool that reads the .mbox and uploads directly. Roundcube then shows it.
On this page
Roundcube shows an inbox, it does not store files
Get this straight and the whole task clicks into place. Roundcube is a webmail viewer, a web page that logs into your IMAP mailbox and shows you what is on the server. It is not a place you upload a file, and it has no real button for importing a whole MBOX. So importing MBOX to Roundcube is not about feeding Roundcube a file, it is about getting the mail into the IMAP mailbox behind it, after which Roundcube simply shows it like any other message. If your Roundcube came with cPanel hosting, this is the exact same thing as loading the mail into that cPanel email account.
You upload the mail to the IMAP mailbox, and Roundcube shows it in the browser.
“The mental model people need is that Roundcube is a window, not a filing cabinet. It shows the IMAP mailbox, so the job is to get the MBOX into that mailbox, and the reliable way is to add the account to Thunderbird and drag the mail across, which uploads it to the server. Most of the people asking this are on cPanel hosting, so the piece to get right is the connection, the incoming server is usually mail.yourdomain.com on port 993, and you use the mailbox password, not anything special. Get that right and Roundcube shows the mail on the next refresh.” Shubham Dixit, Email Migration reviewer (draft, pending approval)
The free way, through Thunderbird
The dependable free route uses Thunderbird as a go-between, since it reads MBOX and speaks IMAP. Install the ImportExportTools NG add-on, right-click Local Folders, choose Import mbox file, and pick your .mbox so the mail lands in a local folder. Next, add your Roundcube mailbox to Thunderbird as an IMAP account using your host’s settings. Once it connects, drag the messages from the local folder into the IMAP account’s folders. That drag uploads them to the server, and they appear in Roundcube on the next refresh. It is free, and it works for any Roundcube, hosted or self-run.
Dragging the mail onto the IMAP account uploads it, and Roundcube shows it.
Your hosting and cPanel settings
The one place this trips people up is the connection, so it is worth pinning down. Most people asking are on cPanel hosting, where Roundcube is the built-in webmail. To add that mailbox to Thunderbird, the incoming server is usually mail.yourdomain.com, the protocol is IMAP on port 993 with SSL, and the username is your full email address. Unlike Gmail or iCloud, a cPanel mailbox normally takes your ordinary mailbox password, not an app-specific one. If you are unsure of the exact server, cPanel’s own Connect Devices page under Email Accounts lists the correct incoming settings to copy.
Roundcube’s own import, for a few messages
Roundcube does have a small built-in import, and it is fine for a handful of messages. Open a folder, use the Import option, and upload .eml files, or a small .mbox on newer versions. The snag is the upload size limit, set by the host’s PHP configuration, which is usually a few megabytes, so a full mailbox archive will not go through this way. Use it to drop in a few saved messages, and use the Thunderbird route above for anything sizeable.
A tool for a big mailbox
If the archive is large, or you would rather not set up Thunderbird at all, a converter uploads the MBOX to the mailbox directly. The PCDOTS MBOX Converter reads the .mbox and pushes it straight to the IMAP account, you point it at the file, pick IMAP, enter the same host, your address and mailbox password, and it uploads the mail to the server for Roundcube to show. It handles the whole mailbox in one pass, keeps folders and attachments, and runs on Windows, with a free version so you can confirm it connects first. Reach for it when the free route feels like too much setup for the size of the job.
The tool route, an .mbox read and uploaded straight to the mailbox Roundcube shows.
Here are the tool steps with the screens.
Step 1. Install and run the software on Windows, then open the menu.
Step 2. Choose MBOX files and add your .mbox.
Step 3. Open Export and choose IMAP.
Step 4. Enter the host, your address and mailbox password, then upload.
To get the pieces down first, see our guide to import an MBOX into Thunderbird. To just read the file before uploading, the free MBOX viewer opens it without a client.
What about a PST
A quick note, since people ask this in the same breath. A PST is not an MBOX, and none of the routes above read it as is. If your archive is a PST, convert it to MBOX or EML first, then follow the same upload into the IMAP mailbox. Our guide to convert PST to MBOX covers that first step, and from there Roundcube sees it exactly like any other mail.
The methods compared
Pick by the size of the archive and how much setup you want.
| Method | Best for | Good to know |
|---|---|---|
| Thunderbird drag to IMAP | Any size, free | Needs the host’s IMAP settings |
| Roundcube’s own import | A few messages | Blocked by upload size limits |
| MBOX Converter tool | A large mailbox, no setup | Windows, uploads in one pass |
Frequently asked questions
Does Roundcube have an import MBOX button?
Not for a whole mailbox. Roundcube can import a few .eml files, and a small .mbox on newer versions, but upload size limits stop a full archive. Upload it to the IMAP mailbox instead.
How do I import MBOX to Roundcube for free?
Import the .mbox into Thunderbird with ImportExportTools NG, add your Roundcube mailbox as an IMAP account, then drag the messages onto it to upload them.
What IMAP settings do I use for a cPanel account?
Usually mail.yourdomain.com, IMAP on port 993 with SSL, your full email address as the username, and your normal mailbox password. cPanel’s Connect Devices page lists the exact values.
Do I need an app password like Gmail?
Normally no. A cPanel or self-hosted mailbox uses its ordinary password. App-specific passwords are a Gmail, iCloud and Yahoo requirement, not a cPanel one.
Can I import a PST into Roundcube?
Not directly. Convert the PST to MBOX or EML first, then upload it into the IMAP mailbox the same way, and Roundcube will display it.
Will my folders and attachments carry over?
Yes. Whether you drag through Thunderbird or use a tool, the folder layout and the attachments inside each message upload to the mailbox intact.
So where does it need to land?
The whole thing gets simple once you remember Roundcube is just the window onto your IMAP mailbox, so every method here is really answering one question, how do the messages get onto the server? If the archive is modest and you are set up in Thunderbird, drag it across for free. If it is a few stray messages, Roundcube’s own import will do. And if it is a big mailbox and you would rather not fiddle with a client, let a tool upload it in one pass. So which of those is your mailbox, and which route gets it onto the server with the least fuss?
