I can connect to tech-xpress.com without problems:
telnet tech-xpress.com 25
Connected to 41850.dsl.gill.wy.vcn.com.
Escape character is '^]'.
220 main.tech-xpress.com ESMTP Postfix (Debian/GNU)
250-AUTH LOGIN PLAIN
Connection closed by foreign host.
Is 18.104.22.168 your public IP address? Is your server in a local network behind a router? What's in /etc/postfix/main.cf?