DaveH,
I do have an ISP which provides me the POP3 account, while my workplace provides the Exchange 2010 (server and) account.
On my PC I use Outlook 2007, where I keep all read POP3 emails (they are deleted from the server), while the Exchange emails are kept on the Exchange server (and a copy on my home PC).
Yesterday I checked my Outlook 2007 settings on my PC and the default email address was the POP3, since I don't want my personal emails sent from home going through the Exchange account.
AFAIK This problem only occurs when I try to send (or reply to) emails from my PC using the POP3 account. If I change the account to the Exchange - I have not noticed any issues.
A partial problem ossurs on my iPhone/iPad2 when replying to emails received to my POP3 account (no such issue with my Gmail/Exchange accounts). I don't think I have problems when composing messages, just the replies.
