Supervisor needs mail from 3 ISPs??!!

Headquarters IT department does not run exchange server. Instead they
have an ISP (ISP#1)and use ISP mailboxes with a company alias.
Supervisor Bill is now transferred to another state. At his new home,
he gets an ISP (ISP#2). Now headquarters transfers his mail from
ISP#1 mailbox to ISP#2 mailbox. When he is at home, it works fine.

Now Supervisor Bill comes to work at new office and wants me to bring
in his mail on his laptop. At the office, we use a different ISP
(ISP#3). At the office, he can receive mail from ISP#2, but can't
send out and reply. Why, because at the office we have to use the
SMTP of ISP#3. If I tell headquarters to route mail from ISP#1 to
ISP#3, then when he is at home, he will be able receive mail, but not
send out/or reply to mail.

How, using Outlook 2002, can I bring in all mail and be able to send
out and reply to all mail? He wants to be able to receive, reply and
send out mail from Outlook whether he is at home or at the office.

Someone, anyone, please help!

Thanks,

Tony