Language is clear on mail-in ballots
3 U.S. Code Section 1 specifies that the electors who select the U.S. president are to be appointed in each state on the Tuesday immediately following the first Monday in November every fourth year.
This is interpreted as meaning the election of electors must occur on that date in every state. Mail-in ballots cast before that date do not comply with the federal statute and should be ignored. Only in-person voting on the date specified should be counted.
Maurice Emmer Aspen