Is my connection to my Postfix server encrypted?

I would like to use my Thunderbird client to send mails trough my Postfix server running on port 25 (SMTP). I would like an authenticated and encrypted connection. I followed these documentations: - http://www.postfix.org/SASL_README.html#auxprop_sasldb - https://wiki.debian.org/PostfixAndSASL#Using_auxprop_with_sasldb It's easy to configure:

$ sudo apt install libsasl2-modules sasl2-bin
$ sudo saslpasswd2 -c -u example.com yugiohjcj
$ sudo sasldblistusers2

$ sudo vim /etc/postfix/sasl/smtpd.conf
pwcheck_method: auxprop
auxprop_plugin: sasldb
mech_list: PLAIN LOGIN CRAM-MD5 DIGEST-MD5

$ sudo vim /etc/postfix/main.cf
# SASL
cyrus_sasl_config_path = /etc/postfix/sasl
smtpd_sasl_local_domain = $myhostname
smtpd_sasl_auth_enable = yes
smtpd_sasl_security_options = noanonymous

$ sudo bash /etc/init.d/postfix restart

Here is how I configure Thunderbird: - Edit > Account Setttings > Outgoing Server (SMTP) - Server Name: example.com - Port: 25 - Connection Security: STARTTLS - Authentication Method: Normal password - User Name: yugiohjcj@example.com When the mail is sent from Thunderbird, I can read this in the Postfix logs:

postfix/smtpd: connect from 1.2.3.4.subs.proxad.net[1.2.3.4]
postfix/smtpd: 39AB821458: client=1.2.3.4.subs.proxad.net[1.2.3.4], sasl_method=PLAIN, sasl_username=yugiohjcj@example.com
postfix/cleanup: 39AB821458: message-id=
opendkim: 39AB821458: DKIM-Signature field added (s=2023, d=example.com)
postfix/qmgr: 39AB821458: from=, size=690, nrcpt=1 (queue active)
postfix/smtpd: disconnect from 1.2.3.4.subs.proxad.net[1.2.3.4] ehlo=2 starttls=1 auth=1 mail=1 rcpt=1 data=1 quit=1 commands=8
postfix/smtp: 39AB821458: to=, relay=gmail-smtp-in.l.google.com[64.233.184.26]:25, delay=0.7, delays=0.08/0.01/0.31/0.3, dsn=2.0.0, status=sent (250 2.0.0 OK  1678874625 bh21-20020a05600c3d1500b003da0d302eb6si1264054wmb.27 - gsmtp)
postfix/qmgr: 39AB821458: removed

So, the mail is received on my Postfix server then forwarded to my @gmail.com address as expected (I am using a ~/.forward file for this). However, I see nothing about encryption. Is my connection to my Postfix server encrypted? If not, how can I fix that please? Thank you. Best regards.