Note post marked Oct 16 meaning two things.
1. The ballot was mailed on time.
2. The envelope is separated from the ballot. The Voting rules require any ballots that has no postmark must be thrown out. The media pushed the narrative they where "only envelopes"
Right on top of the list of safeguards. "ballot AND envelope"
https://www.cisa.gov/sites/default/files/publications/mail-in-voting-election-integrity-safeguards_508.pdf
found here