Identity Selection in the Compose Window
Here's how Identity selection works when using the Compose window.
The send Identity that will be selected when you open the Compose window is based on the account that you have selected when you click the Compose button. If you have multiple Identities assigned to that account, Postbox will select the default Identity, which is the first Identity that is created when you setup the account. To switch Identities, use the Identity bar in the Compose window, which is located above the To: addressing field.
If you have an Account Group selected, then the Identity selected in the Compose Window will be from the first account listed within the Account Group, and the default Identity for that account.