Upgrading from 13 to 14 while keeping sendmail

From: Garrett Wollman <wollman_at_bimajority.org>
Date: Fri, 31 Jan 2025 17:36:47 UTC
I have a bunch of machines running 13.4 that I need to eventually get
to 14.x.  What's the recommended way to do a source upgrade while
preserving existing (working) sendmail MSA/MTA configuration?

-GAWollman