During 2016 Yahoo rolled out a new way to authenticate which is considered a superior way to the one supported before and we are happy they joined Gmail & Outlook to support this authentication standard.
Shortly after, we have introduced support for Yahoo OAuth 2.0, allowing you to utilize the latest security enhancement.
Do you need to take any action?
It depends on when you added your Yahoo account to BlueMail. If you received an email from Yahoo with the subject “…” that is related to BlueMail, you can remove and re-add your account to be able to use the new OAuth authentication mechanism from Yahoo.
You can read more about Yahoo new App Access and Security here. BlueMail is fully compliant with the More securely access defined by Yahoo, so in case you received their email, simply remove and re-add the account in BlueMail.