Trump signed an executive order today about mail in voting. It's an attempt to restrict postal delivery of mail in ballots to people on a DHS-compiled list of citizens.
Rick Hasen has a nice summary (tl;dr: not much to get worked up over here, for both legal and practical reasons):

Breaking: President Trump Signs New Executive Order on Elections: It is Underwhelming Compared to What Was Threatened. It's Key Part is Likely Unconstitutional: Directing the Post Office to Reject Mail Ballots Except from Those on Federally Approved Voter Lists #ELB
President Trump has signed a second executive order purporting to regulate federal elections (especially mail ballots). His first executive order from last August has already been enjoined in key parts for violating the Constitution. As Judge Kollar-Kotelly wrote in one … Continue reading Breaking: President Trump Signs New Executive Order on Elections: It is Underwhelming Compared to What Was Threatened. It’s Key Part is Likely Unconstitutional: Directing the Post Office to Reject Mail Ballots Except from Those on Federally Approved Voter Lists →