Mail aliases (or pseudonyms, synonyms) are different addresses which refer to the same mailbox.
For example, each mailbox on Yandex Mail has aliases in @yandex.ru, @narod.ru, @yandex.ua, @yandex.by, @yandex.kz, @ya.ru and @yandex.com domains. Emails sent to any of these addresses will arrive at the same mailbox.
You can add an alias to any of the mailboxes on the domain. To do this:
After this, emails sent to the addresses which were added as aliases will arrive at the main mailbox.