Problem

there is a SMTP server error reported in the log message:

Error ... Ivara.Mail.SmtpPlugin.SmtpMessage [14] SmtpMessage::Send() - exception thrown EXCEPTION OCCURRED:AuthenticationException The remote certificate is invalid according to the validation procedure.    at System.Net.Security.SslState.StartSendAuthResetSignal(ProtocolToken message, AsyncProtocolRequest asyncRequest, Exception exception)

Solution

The setting for encrypting the email is the problem (SMTP Enable TLS). Somehow the SMTP Enable TLS setting appears to be defaulted to True in the R711 settings. This setting didn’t exist in 7.8 and after the upgrade it got enabled automatically by default. After turning it off, emails started to get through.

The setting can be found here in the Ivara Configuration tool's Full Settings for the Service: