Zoho IMAP: Opera complains about low encryption level

Zoho IMAP: Opera complains about low encryption level

Since last week or so, everytime the mail client in Opera starts I get a dialog as shown in attachment. On the next tab the message is "The server is using a short public encryption key which is not considered secure". I am only using imap for incoming messages, using imap.zoho.com on port 993, TLS enabled. Did anything change in the zoho mail system? Is there something that I can do about it?