Mailgun will no longer support TLS 1.0/1.1, does this affect CiviCRM Smtp
For SMTP Civi by default uses pear::mail, which uses Net_SMTP. The current version of Net_SMTP that civi has supports TLS 1.2. See https://github.com/pear/Net_SMTP/blob/18b5dbaa049bee5f6d02c9a4318db02472e2c922/Net/SMTP.php#L613
It also depends on the version of the openssl extension you have installed in your php. If you run php -i | grep -i openssl or look at the output of phpinfo, you most likely have newer than openssl 1.0.1 so should be good.