This has been fixed as of CA Performance Management 3.7.10, from the 3.7.10 Fixed Issues section of the documentation:
Symptom: When sending email via STARTTLS, Performance Center would only allow TLSv1.0. If email server was TLSv1.1 or TLSv1.2, the email server would reject the email connection.
Resolution: Updated Performance Center to support TLSv1.2, TLSv1.1 and TLSv1.0 when email server supports STARTTLS.
Disable TLSv1.2 and/or allow TLSv1.0 on the email server.