And here is the solution: I had to explicitely tell the smtp proxy to NOT use tls by specifying
-o smtpd_use_tls=no
-o smtp_use_tls=no
-o smtpd_tls_security_level=none
-o smtp_tls_security_level=none
where it seems that simply setting smtpd_use_tls and smtp_use_tls to no
was not enough! The additional smtp_tls_security_level set to "none" was
also necessary
Thank you for your patience and help! Regards Dietrich
