Measure open rates for standard emails from Civi, not from Civimail
Not sure you'd class this as cunning or hacky but we have a trick &amp; some code. Essentially we've changed scheduled reminders to send from CiviMail rather than triggering it's own one-shot emails. Workflow something like this


Set up a regular email in CiviMail complete with tracking
Send to a test group of internal emails
Set up your scheduled reminder, with our code the interface can now select previously sent CiviMail emails instead of building the email in Scheduled reminders
What ever triggers the email triggers it and the corresponding email adddress is added to the email spool for the CiviMail email, next cron Civi notices the spool has one more email compared to sent emails and sends it's to the extra email.


It's not perfect as the activity date is on the original CiviMail send, which is something I want to clean up. Talk to Parvez @ Veda he should be able to supplt you with the code.