Major democratic countries that allow mail-in (postal) voting - Australia, Austria, Canada, Finland, France, Germany, Greece, Hungary, India, Indonesia, Italy, Malaysia, Mexico, Norway, Philippines, Singapore, Spain, Switzerland, United Kingdom and United States.
Russia’s postal service is a notoriously under-performing organization. They could not be counted upon to deliver the ballots much less get completed ballots back to collection locations. The other reality is that Russia is not a democratic nation and under Putin your vote is meaningless. Russian Postal Service among World's Worst https://daijiworld.com/news/newsDisplay?newsID=141472