Hi again, and sorry for my late reply...
The reasoning for setting the task to run once every minute, was purely for testing purposes.
We have also tried running it once every hour, but this did not change our outcome.
The emails never showed up.
Yes, we based our findings on the general log. From there we could see that the "CustomAttributeDate10"-field was cleared, but there was no records (via general log) of emails being sent based on the previous action. All of our email-settings (including recipients) were copied from another working action.
Is there a script that perhaps may be more reliable in doing what we originally set out to to?
That is; to trigger an email once the "accountExpires"-field in AD goes from no value to some value.