Ok - let's get a little clarification here.
First, techincally 'Quick Attach' is the feature in Act! 2009 and 2010 where a user selects one or more INBOUND emails in outlook and then clicks the button 'Quick Attach' in the Outlook tool bar.
This does not sound like the feature you are referring too, as I believe that you are concerned about your users creating OUTBOUND emails and having them automatically attach to the contact recipient.
So, that also rules out Outlook Rules. Rules only apply for INBOUND mail (in most cases), and emails can be attached regardless of whether there is a rule or not - as you already discovered.
I beleive what you are looking for is the users' email preferences in Act!.
Go to the Preferences wizard from the Tools menu. From there select the Email tab.
Click Email System Setup.
Walk through the wizard, changing nothing, until you get to the page entitled 'Email - Record History'. I am pretty sure that is set to any one of the chioces other 'None'. Change it to 'None'. Finish out the wizard being sure to change nothing else.
What you have told Act! to do, is that when an email is created - whether directly in Outlook OR from within Act! by clicking the email address, BY DEFAULT, DO NOT CREATE HISTORY.
This does not mean you cannot create history - just that you have to specify you want to within the Outlook Create email screen. If you are using Outlook 2007, you will have an Add-ins tab where you will find an Act History setting where you can change from None to another choice if email history is desired. In Outlook 2003, as memory serves, it is visibile already above the send to fields...
In short - instead of history always being created, the user will now choose when it is so.
BTW - this change will not affect how inbound email is handled with Quick Attach or with rules....
