This is dumb but I'll ask anyway.
Lets say you have a laptop using Outlook to read e-mail from an outside POP3 host.
You bring the laptop to the office and login locally and read your e-mail normally.
What if you login in to the office Windows Active Directory domain ( new profile)
and then try to read your e-mail from the outside POP3 host.
What is the result ? Do you get out of sync and have some e-mail in one profile and some e-mail in the other profile ?