What is the new secure data transfer protocol from Yandex?

Question

Yandex

The other day there was a mailing from the Yandex.Mail team with the subject "Yandex.Mail Security Service recommends updating email programs by April 25, 2016". The letter said about the need to update, because. soon the old mailers won't be able to work with their new secure protocol.
Who knows what it's all about? What is the new protocol?

Answer 1

In older versions, the certificates used in TLS encryption are signed with the insecure SHA-1 algorithm. In newer versions, this algorithm has been replaced with SHA-256, which provides a higher level of protection for connections between email programs and Yandex.Mail servers.

https://yandex.ru/support/mail/mail-clients/sha-256.xml

Answer 2

STARTTLS.
Alternatively, smtps/imaps/pop3s.