Unable to start STARTTLS in PowerMTA server

We have PowerMTA v5.5r1 installed on Ubuntu 22.04 server. When I tried to telnet localhost with 25 port I am unable to see 250-STARTTLS option.

Please help which parameter or configuration needs to update?

In /etc/pmta/config file there are multiple entries however I want to check is STARTTLS is enabled for my localhost. The 12.12.12.12 is my localhost ip.

<source 12.12.12.12>
    always-allow-relaying yes
    log-connections yes
    smtp-service yes
    allow-starttls yes
   #require-starttls-before-auth yes
</source>

smtp-listener 12.12.12.12:25

In below output when I tried to telnet my localhost IP with 25 port I am not able to find 250-STARTTLS option.

 root@localhost:~# telnet 12.12.12.12 25
 Trying 12.12.12.12...
 Connected to 12.12.12.12.
 Escape character is '^]'.
 220 mydomain.com ESMTP service ready
 ehlo 12.12.12.12
 250-mydomain.com says hello 
 250-ENHANCEDSTATUSCODES
 250-PIPELINING
 250-CHUNKING
 250-8BITMIME
 250-AUTH CRAM-MD5 
 250-AUTH=CRAM-MD5
 250-XACK
 250-SIZE 0
 250-VERP
 250-SMTPUTF8
 250 DSN
 quit
 221 2.0.0 mydomain.com says goodbye

Expected output will be:

[root@localhost ~]# telnet 12.12.12.12 25
Trying 12.12.12.12...
Connected to 12.12.12.12.
Escape character is '^]'.
220 mydomain.co.in ESMTP service ready
ehlo 12.12.12.12
250-mydomain.co.in says hello
250-STARTTLS

You probably can't support TLS / STARTTLS when you don't have a certificate defined (somewhere). Your config needs for example:

smtp-server-tls-certificate FILENAME PASSWORD
smtp-server-tls-ca-file /path/to/some/certchain.pem