2) Since for certain reasons this question is extremely important to me, I have researched it for many hours and multiple times, and I did not find even one single example of a virtusertable entry where the RHS is a file.
So I would be very grateful if you could point me to an appropriate reference, or if you could discuss that question with the Sendmail team and eventually fix or clarify the manual. In any case, could you please let me know the results?
P.S. When replying, please make sure that your message gets authenticated by SPF or DKIM; otherwise, my spam filters won't let it through.