Labels and folders keep your mail sorted. Gmail uses labels, and Outlook and other accounts use folders; Newton shows both in your account's folder list. You can create them in the desktop app, and create, rename or delete Gmail labels and Outlook folders on your phone or on the web.
Steps
Desktop
In the sidebar, hover over or click an account under All Accounts to see its folders. With only one account, its folders are already in the sidebar.
Click + (Add folder) below the account's standard folders.
Type a name and press Enter.
To add a subfolder, hover over a folder and click its + (Add subfolder).
To file an email, press M or right-click it and choose Move to, then pick the folder.
iPhone, iPad & Android
Open the menu and tap the Settings gear at the bottom.
Tap Accounts, choose a Gmail or Outlook account, then tap Manage labels.
To create a label, tap + at the top (on Android, tap New label). Type a name, pick an icon and tap Add.
To rename a label or change its icon, tap it, make the change and tap Save.
To delete a label, tap it and tap Delete Label. On iPhone you can also swipe left on it.
If you have more than one account, choose the account from the menu.
Under New Label, type a name, pick a color and click Create.
To rename or delete a label, hover over it under Custom Labels and click the pencil or the trash icon. Click a label's icon to change it.
Good to know
In Gmail an email can have several labels; in Outlook an email sits in one folder. Moving an email adds the new label or folder and takes it out of the one you're viewing.
Labels and folders are saved in your Gmail or Outlook account, so changes show up there too. Label icons are a Newton extra and show on all your devices.
Deleting a Gmail label keeps the emails. Deleting an Outlook folder moves the folder and the emails in it to Deleted Items.
Only the desktop app can create subfolders or add folders to IMAP accounts. IMAP folders can't be renamed or deleted in Newton.