Exchange won't send when offline now that POP3 Account exists

[mikelee101]

Hello,
Outlook 2003, WinXP Tablet Edition, SP2.

I use Outlook to connect to our Exchange server. I will occassionally
compose an email and then schedule it to send at a later time. This worked
great, even if Outlook was closed at the scheduled time.
This week, I had to add a POP account to Outlook. Now, Outlook won't send
using the Exchange Server account when Outlook is closed. Here are some of
the things I've tried:

-Set up a Send/Receive group with only the POP account in it, and set this
group not to Send/Receive when offline.
-Removed the POP account from the All Accounts group, so that only the
Exchange account remained in this group. I didn't change any settings on
this group.
-Set the Outbox folder to either be available or unavailable offline.

I've tried those independently as well as simultaneously. Then I deleted
the POP account, and now it works the way it used to again. So, my question
is:

Is there a way to keep the "send when closed" functionality with the
Exchange Server account with a POP account also resident in Outlook?

Thank you very much to all.