There have been drop boxes at various locations in Oregon, prior to the last election. No postage or postmark required. The last election was the first one to be postage-free.
States that conduct all elections by mail:
Colorado (CRS §1-5-401)
Hawaii (Hawaii Stat. §11-101)
Oregon (ORS §254.465)
Utah (Utah Code Ann. §20A-3a-302)
Washington (Rev. Code of Wash. 29A.40.010)
Other states that allow some form of mail in voting:
https://www.ncsl.org/research/elections-and-campaigns/all-mail-elections.aspx