I have an outlook.com account that pulls in email from an imap/pop email account.  I use outlook.com to sync up the email address to all of my devices (i.e. computer, iPhone, iPad).  Just recently, my Outlook 2013 on my laptop began sending outgoing email as "on behalf of."  The account is configured on outlook.com to send and receive mail (not a send-only account).

My iPhone and iPad both send correctly.  Can someone please help me?