After an upgrade to 20.2.1+, emails from CAPC will not work if your email server advertises STARTTLS until you import the SSL certs into CAPC.
https://knowledge.broadcom.com/external/article/187195/
Our email servers do not use SSL certs, can we disable this feature?
How to disable STARTTLS normally used for email sends in DX NetOps Performance Management Portal web server.
All supported DX NetOps Performance Management releases
In 20.2.1 we made a change to enable STARTTLS by default. If the email server advertises STARTTLS we will always use it.