The Netherlands. The only exception are people abroad and the upcoming election (due to corona the elderly ill and some others are allowed to vote by mail. Not the general population).
Not only that, we're only allowed to vote when you have a voter ID and an ID (passport or drivers licence are also allowed). You can vote for others, but you need their voter ID and a copy of their ID to vote. Besides you're only allowed to vote for one other person.
So if you're going into semantic it technically isn't banned for people overseas. But it is for people living in the country itself.
They were allowed in the Netherlands until 2010, when a lot of errors and irregularities were found during an election. When you vote here there are chained red pencils at the polls with which you have to vote (ballots are anonymous). Still fraud can happen during the counting of the ballots, but still better than voting machines.