Mystic Email Servers - SMTP, POP3 is working

Hello All,
Ok I can see in the logs that the POP3 login is working, I get a success, see 
that i do login.
However, SMTP is giving a certificate error:
Authentication failed. Please check your username/password.
Server returned error: "TLS Negotiation failed, the certificate doesn't match 
the host. For more information, goto 
https://support.google.com/a/answer/2520500, code: 550".
Not much help from that google support page, it doesn't exist.
What is the certificate and where is it?

Baffled.

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