I have an Office 365 account and I connect to it using Microsoft Outlook 2013. I use this account for business correspondence. I also have another business account, which is POP3, that my Office 365 account will also receive messages from. So, Office 365 hosts my default email account, and also accepts POP3 messages from another email address.
The problem is that when I reply to a message (using Outlook) that has been received from the POP3 account, customers receive messages that inform them that the message was received from a different account and that I am sending on behalf of this other account. I don't want anyone to see or know this.
How do I setup Office 365 and or Outlook so that when I reply to a message that is received from my POP3 account that no one sees that I am replying on behalf of another account?