Is there such a thing that you can get entourage to ask you if you received
a response for a message you sent previously - without setting up a task or
a calendar event?
No. Do you mind explaining how you see that working? You've probably sent
1000 messages in the past month or two - do you really want 1000 reminders
every 5 minutes? Or you want to be able to trigger a switch just before you
send a message that says: "Ask me in [x ] [days/hours/minutes] if I've
received a reply to THIS message?" And then another switch that can turn it
off or snooze it to ask again after it appears?
How about a script (you'd just need to press a keyboard shortcut to run it)
that opened a new task for you with the name of recipient in the Title as
"Message Reminder [Recipient Name]" and the message subject and date/time
sent in the note, with a default reminder time you can have set and can also
change yourself? You can snooze the reminder when it appears, in the usual
way, or mark it complete. The script can also link the sent message to the
task, so you can always click "Open Task" then "Open Link" if you want to
fetch the message to resend it.