Your Default Email Account is used to send all outgoing messages. When you choose a Default Account, it will be listed in the 'From:' field of all new and outgoing messages, and any replies to your message will be sent to this address.
To change the Default Account, do the following:
- In the main IncrediMail window, click the 'Tools' menu (marked below in red) and then 'Email Accounts…' (marked in blue).
- Select the Email Account you wish to be Default (it will be highlighted after choosing), and click 'Set as Default' (marked in red).