I posted this over on Fascist Book ... some research on the mail in ballot deadlines:
270 ELECTORAL VOTES TO WIN.
Ballots requested and outstanding need to be counted and accounted for. Late ballots should not count, you have plenty of time to get the ballot and get it in. Here locally you can personally take a mail in ballot to the court house and hand to clerk or a secure drop box inside of courthouse. There is still 6 or so weeks and no reason people cannot plan on getting their vote there in time, or to vote in person like V.P. Biden managed to do.

Many states have mail in ballots for voting on a regular basis. A Trump backed Californian congressional special election was heavily mail in and the Republican won. I think it was Los Angeles. So it is not new, what is new is state like Nevada trying to do unrequested ballot drops, trying to allow ballot harvesting. Regular mail in is you request the ballot yourself to verified home address using verified state ID (driver's license where you proved address and citizenship with a birth certificate). That is just like absentee just it allows by request for any reason and is common and IMO not too different than in person where often I did not have to present my ID, only gave my name and address.

STATES THAT REQUIRE BALLOTS ARRIVE BY ELECTION DAY. Thirty states and Trump won 21 of those last time (Maine was split).
Alabama 9
Arizona 11
Arkansas 6
Florida 29
Indiana 11
Idaho 4
Kentucky 8
Louisiana 8
Maine (3 but- split delegates not sure if Trump had 1 or 2 in 2016 – looks like 2)
Michigan 16
Mississippi 6
Missouri 10
Montana 3
Nebraska (split possible but Trump won all 5?)
Oklahoma
Pennsylvania 20
South Carolina 9
South Dakota 3
Tennessee 11
Wisconsin 10
Wyoming 3
(190 if Trump only had 1 from Maine 191 if 2 I think 2 is correct though)…
Colorado 9
Connecticut 7
Delaware 3
Hawaii 4
Massachusetts 11
New Hampshire 4
New Mexico 5
Oregon 7
Rhode Island 4
Vermont 3

BALLOTS postmarked either day before or day of election that can arrive after election day (but if outstanding less than differential these states can be called election night as well).

Ballots mailed must arrive the day after election:
Texas 38 (191+38 is 229 Trump if all same per above)

Ballots arrive by 3 days after
Georgia 16
Kansas 6
North Carolina 15 (Trump won all these 229+16+6+15 = 266)
Virginia 13

Five days:
Washington (state) 12

Six days:
Iowa 6 (266+6=272 electoral votes and latest this should take, if picks up some prior blue states and clear victories can easily be called on election night)
Utah 6
West Virginia 5

Seven days:
Minnesota 10
New Jersey 14
New York 29

Ten days:
Alaska 3
Ohio 18
D.C. 3
Maryland 10

Fourteen days
Illinois 20

North Dakota post mark 1 day before election, no specific arrival.

longest other states would be   California post mark by election day, receive in seventeen days … 55
and Nevada postmarked on or     before election day, no arrival date given 6 vote                                                                                  Trump won electoral without those two    states prior CA and NV so even if they try to inflate popular weeks     after, doesn't matter if he has the electoral college won.  That is    the Constitution.   If people don't like it they need to change    that, but it is there for a reason.   Glad we have it so that the   entire county is not literally on fire.

Information obtained from : [vote.org]
[amp.businessinsider.com]