It's been a busy night fixing various bugs on the thisshitistemp.com server. Here's a collection of useful information for future reference.
smtpd_tls_security_level
Don't force Postfix stmpd encryption if you want other mail servers to be able to talk to you. Use
smtpd_tls_security_level = may # allow incoming encryption
instead of
smtpd_tls_security_level …