For anyone still doubting mail voter fraud:
The Spanish government (socialist-communist, how surprising....) was recently caught trying to do the same to the upcoming elections in Madrid.
Note that it says "votos emitidos" (votes sent) despite the customer not actually casting any vote (customer only sent an ordinary letter).
Funny enough the head of Correos (public mail service of Spain) was part of the current ruling socialist party.
You can find this all over the Spanish news networks (just do a little bit of Googling).