This is a short (14 min.) video interview with the King County Elections Director How Secure is Vote by Mail? Note, King county has over a million registered voters and the last report I heard on Wednesday was that 300,000 ballots had already been returned-- note, Washington State is all vote by mail.
A longer version (24 minutes) with more detail is in this Disaster Zone Podcast, How Secure is Vote by Mail?
Both are worth your time to view or listen.
I voted already--how about you?