Roundcube’s interface is fairly intuitive. Like most email clients, Roundcube opens your inbox by default. You got your email folders in the left pane, followed by a list with emails and a pane that displays individual emails.
Image: viewing the email@example.com inbox in Roundcube
Some things in Roundcube don’t work as you you might expect. For instance, email programs usually let you sort emails by clicking on headers such as “From”, “Subject” and “Date”. These headers are not shown in Roundcube. To sort emails you need to instead click on Options and then select how you want to sort your emails.
If you prefer a more traditional interface, you can change the theme via Settings » Preferences » User Interface » Interface Skin.
Image: Roundcube’s “Larry” skin.
The search field above the list with emails lets you filter emails. You can narrow down your search by clicking on the down arrow to the right of the search field. By default, Roundcube searches the “Subject” and “From” fields.
There are a few interesting options for selected emails under More:
You can write a new email by clicking the Compose button. By default, Roundcube uses plain (unformatted) text for emails. If you prefer to use HTML then you can click the HTML button (below the “Subject” field).
Image: writing HTML email in Roundcube.
If you want to always use HTML, you can change this via Settings » Composing Messages » Compose HTML messages.
Roundcube doesn’t let you view the size of all your email folders. You can see the total size of your mailbox by clicking on the disk usage box at the bottom of the folder pane. This shows the overall disk usage for both your mailbox and your cPanel account.
Image: Viewing the disk space usage for both an email address and the cPanel account.
To get more information about an individual folder you can select Folder actions (the three vertical dots at the top of the folder pane) and then Manage Folders. You can then select an individual folder. To see the size of the folder you need to click the Click to get folder size button.
If you want a breakdown of all email folders, including the number of emails and the size, then you can instead use cPanel’s Email Disk Usage interface.