I too am having similar issues. I have Postfix running on fedora 9 that I installed using rpm. I am also using dovecot and squirrel mail. I can send and receive email fine, but authentication takes place in plain text which is a security issue. I have tried setting up TLS and SASL but they both fail. On my last attempt with TLS I got the following errors:
warning: cannot get certificate from file /etc/postfix/postfix.cert
Dec 16 21:53:01 mailtest postfix/smtpd[6142]: warning: TLS library problem: 6142:error:0906D06C:PEM routines:PEM_read_bio:no start line
em_lib.c:647:Expecting: CERTIFICATE:
Dec 16 21:53:01 mailtest postfix/smtpd[6142]: warning: TLS library problem: 6142:error:140DC009:SSL routines:SSL_CTX_use_certificate_chain_file:PEM lib:ssl_rsa.c:727:
Dec 16 21:53:01 mailtest postfix/smtpd[6142]: cannot load RSA certificate and key data
Any help or guidance is much appreciated.
Thanks