The list of existing mailboxes and their settings are available by clicking the number of mailboxes to the right of the domain name. To create a new mailbox, go to the My domains page and click Add a mailbox under the domain name. Enter the name of the new mailbox and the password. The username and password for the new mailbox must conform to the Yandex requirements:
To send email from the new mailbox, the owner must log in to Yandex.Mail at least once using the username "<mailbox name>@yourdomain.tld" and the password you set.
You can create any valid mailbox names except abuse@ and postmaster@. Email sent to these addresses is redirected to the Yandex support service for responding to complaints about spam from your domain.
To receive these emails along with the support service, create a mailing list with the address abuse@ or postmaster@ and add the desired addresses to it.