Oregon is the only state in which all voting is by mail. Washington lets each county decide whether to use all-mail voting. Now North Dakota seems likely to join Washington. On February 27, the legislature passed SB 2230, which lets each county decide whether to use all-mail balloting in both general and primary elections (previously, North Dakota counties could use all-mail voting in primaries, but not general elections). The North Dakota Governor hasn’t signed the bill yet.
A similar bill has been introduced in California, AB 1654 by North Bay Assembly Member Jared Huffman. No clue yet how far it will get.
I think Vote By Mail is a good idea.
Since Oregon established it there have been moderately greater voter turnouts, lower election costs, and a valued paper trail for audits.
Surveys of Oregon voters show most people there think the benefits with this new voting system outweigh the negatives.