When I reply to a mail message, the reply is sent using the default email address as defined in mail.app, and not the email address that it was originally addressed to.
I have all accounts correctly set up and active.
To make it use the correct address, I need to manually select the account I want to send the email through. I am using OS 10.8 recently updated it. It did not happen with previous OS.
Best Answer
This may be because a certain account is locked into a particular SMTP server.
Mail
->Preferences
Accounts
tab.