Error verifying the sender

If you have sent a message from your Yandex mailbox and received a non-delivery report that states the following: “501 5.5.4 ‘Wrong param’, this means there was an error verifying the sender.

To resolve the problem, contact the administration of the recipient's mail service and ask them to enter Yandex.Mail email addresses into the whitelist of the sender verification service.

Note. If you use Yandex 360 for Business, the SPF record must be set up on the linked domain.