We are running Exchange 2003; we have our staff setup with 2 email addresses: one internal (firstname.lastname@example.org) & external (email@example.com). The internal account uses our Exchange server to send mail around the office. Our external account is managed by our ISP. If a user sends external mail using their internal account the recipient receives the mail but cannot reply since the reply to address is private/internal to our network. We use Outlook as our mail client & the default account to send mail is set to External. Occasionally, Outlook (or Exchange; not sure where the switch is happening) will send mail via their internal accounts & clients complain because they get a mail admin error when replying: "firstname.lastname@example.org cannot be found".
Where could the problem be lying that would switch the default account from External to Internal? Outlook or Exchange?
Thanks for your time,