Can I create subfolders in my mailbox?

Folders in Cirrux are labels. To nest one under another, put a slash in its name: Work/Clients shows up as Clients under Work in the sidebar. You can go as deep as you like, for example Work/Clients/Acme.

Create a subfolder

1. In Cirrux Mail, go to Settings → Mailboxes and pick the mailbox.
2. Open the Labels tab and click Create label.
3. Enter the full path, such as Work/Clients, and click Create label.

If Work doesn't exist yet, it's created too. You can also create a label while filing mail: choose Label... on a message and type the new name, slash included.

To move a folder, open its menu on the Labels tab, choose Edit and change the path. Renaming Work/Clients to Projects/Clients puts it under Projects, and the folders inside it move along.

Under Inbox or another built-in folder

A label that starts with the name of a built-in folder nests under it. Inbox/Receipts appears under Inbox in the sidebar.

In other mail apps

Over IMAP, in Apple Mail, Outlook or Thunderbird, your labels show up as nested folders with the same structure. Creating a subfolder in one of those apps creates the label in Cirrux too.