Bitrix24 doesn't support integration with Yandex.Mail anymore.

But if you have some mailboxes connected (via Yandex.Mail) earlier, you can still use them.

In this case, you own a domain (you manage a domain with your registrar), but Bitrix24 is a domain administrator in Yandex.Mail.

How to get administrative access in Yandex.Mail

1. Go to Yandex Support page. In the Domain management access section, scroll down to I forgot or don't know what the domain administrator account is.
   
2. Click Feedback and select I need to restore access to domain management.
   
3. Fill the rest of the fields with the necessary information.
   Please note that a domain can only be connected to a login@yandex.tld type of Yandex account. No other mailbox can be used.
4. Yandex will send you an email with detailed instructions on how to confirm domain ownership.
5. After all the steps have been completed, ownership of the domain is transferred to the account that you specified in your request.

Now you can manage your Yandex.Mail mailboxes!