How do I sort my messages into folders?

Just like in a binder: create your own folders (“Invoices”, “Projects”…) and file your messages in them.

The demonstration (25 seconds), without sound: read the captions under the picture (in French, like the app). The people and addresses are made up.

Step by step

To create a folder: in the folder column, hover over the name of your mailbox (« Messagerie » (Mail) or your address) and click the little + that appears on the right.
Type its name in Nom du dossier (Folder name), then click Créer (Create).
To file a message there: open it, click Déplacer vers un dossier (Move to a folder) (above the message, on the right), then the folder you want.
Even simpler with the mouse: grab the message in the list and drag it onto the folder.
To rename or delete one of your folders: right-click its name, then Renommer (Rename) or Supprimer le dossier (Delete folder). Nouveau sous-dossier (New subfolder) creates a folder inside it.

Archiver (Archive) (the little box above the message) files the message in the Archives folder in one click.
The built-in folders (Boîte de réception (Inbox), Envoyés (Sent), Corbeille (Trash)…) can’t be renamed.