It took me a few days to get back to everyone. Here's what I have found out.
First, the "Suppress validation of 'From' field..." option does affect whether the filters are applied. As an experiment, I enabled suppression, and no longer received notifications of invalid addresses. Instead, notification was skipped and my filter deleted the email, as shown below.
Fri 15, 12:22:24: Job MG00003B: sender address 'charlesnn@softwaremeadows.com' is invalid
* Job killed by filtering rule.
To prove it, I disabled only that setting, and began receiving notifications again.
Fri 15, 13:56:45: Job MG00004F: sender address 'charlesnn@softwaremeadows.com' is invalid
Fri 15, 13:56:56: Job MG000051: from <> (local)
* Recipient <charlesnn@softwaremeadows.com> unknown
Fri 15, 13:56:56: Job MG000051: Processing failed deliveries and generating notifications
Mail Delivery System <> - Notification discarded - potential loop.
Fri 15, 13:57:07: Job MG000053: from postmaster@flattland.com (local)
To: charles (local) -OK
With that said, based on Thomas' advice, I'm going to
- Disable "Suppress validation of 'From' field...", which is the default
- Disable "Accept mail for invalid local addresses", which is also the default. I had it enabled because, at one time, I accepted any email to the domain.
Thanks for the help. If I run into trouble, I'll post again.
Charles