I have been googeling for days! I have a cert from rapidssl. I read up that the problem with num=20, is that indicates it doesn't know the issuer, or doesn't know the ROOT Cert, right? I run this command: openssl s_client -showcerts -connect smtp.server.com:465 I get this error: verify error:num=19:self signed certificate in certificate chain Here is what i have in my postfix main.cf, and what i have done: smtpd_tls_key_file = /etc/postfix/ssl/smtp.server.com.rsa.key (this is the private key) smtpd_tls_cert_file = /etc/postfix/ssl/smtp.server.com.PUBLIC.key (this is the public key given to me by rapidssl) smtpd_tls_CAfile = /etc/postfix/ssl/combo.csr.key This key has both the intermediate keys ON TOP, and the ROOT KEY on the bottom. Here is the Intermediate keys: https://knowledge.geotrust.com/library/VERISIGN/ALL_OTHER/geotrust%20ca/GT_QuickSSL_and_Premium_and_Trial_intermediate_bundle.pem and here is the root CERT: http://www.geotrust.com/resources/root_certificates/certificates/Equifax_Secure_Certificate_Authority.cer anyone know how to use rapidssl certs?