This document describes how use multiple email accounts in Outlook. It assumes that you have configured Multiple Email Accounts and Individual Email Inboxes, as described in the accompanying documents.
New Mail Message
You can use Outlook just like normal, once you have created a "New" mail message as shown in Figure 1. a "New Mail Window".
Figure 1.
At anytime, before sending the message, you can change the account that is going to be used to send.
Figure 2.
As shown in Figure 2. the "Account" button will let you select an account from the list you have added already. This change will be shown in the top of the "New Mail Window", as Shown in Figure 3.
Figure 3.
This will set the From Email Address and the From Name to those set for that account when you added the new Accounts.
Replying to / Forwarding Messages
When using the "Reply", "Reply to all" or "Forward" buttons to send an email. Outlook will automatically set the Account to the one that received the email.
Again, the top of the "New Mail Window" will show you which account is being used to sent the message. And using the "Accounts" button you can select to send it via another account.
Setting the Default Account
It's likely that you will use one account more any others. You can set this to your default account. As Shown in Figure 4. "email1@domain.tld" has be set as the default account.
Figure 4.
To change the default account, select another in the list and click the "Set As Default" button.
Once set, when you create a new mail message the default account will be selected.