I have Microsoft Outlook. I have two emails address which is pulled in my
inbox. Say Email1 and Email2.  Email1 is the default one.

When I get a email from Email2 account and try to respond that its not able
to deliver the message as it tries to send the Email2 using Email2's outgoing
server. I have to every time manually change the account option to Email1
Account in the top panel of the compose screen to send it from the Email1.

Can this be made default(Email1 Account for sending).

I have a rule in my inbox which forwards wat ever mail i get to my personal
gmail account. Due to this, the mails which I receive thro Email2 to Inbox is
only in OUTBOX(forwaded one thro rule) and not able to send them
automatically. But the ones delivered thro Email1 are automatically forwarded
to that gmail email address(as its the default).

FYI Tools -> Email Accounts says (Email1 is default)

regards
Srivaths