Russia’s Federal Tax Service (FTS) has published guidelines for taxpayers on sending emails to government agencies.
According to these guidelines, emails should only be sent using mail servers in Russian domains such as .ru and .su, as well as countries that do not fall under restrictions.
In order for the letter to reach the recipient, it is recommended that you check your email address before sending it: accepting emails from sender domains whose countries of origin are the United States and European Union countries is now blocked.
The press office gives this explanation:
This was done in accordance with the recommendations of Russia’s Federal Service for Technical and Export Control to protect the FTS email service from external negative influences (computer attacks, malware, and so on).”
As the Federal Tax Service notes, such restrictions will apply to other government agencies as well. Apparently, Mail.ru and Yandex.Mail can be used safely, but emails sent using Gmail are likely to be blocked.