Windows XP multiple mail accounts not behaving

[msoedave]

I have a PC running under XP with 3 user accounts. It recently required a re-install of XP and I had to set up the 3 accounts again. In each case I used the "mail account set up" wizard in Outlook Express to create different mail accounts with the 3 different email addresses. In each case they are all using the same Account Name (which is my email address) & Password that my service provider requires. However ... my wife's mail account seems able to send emails successfully but it fails to receive replies that I know have been sent to her. On the other hand, she has received emails addressed to me ! It seems that if she is logged in then she receives my emails whereas I receive them if I am logged in. I've checked the mail accounts many times and I'm sure I've set them up as required ..! Help please ?!