depth = 0
issuer = /CN=RSA issuer CA
subject = /CN=mx1.example.com

depth = 1
issuer = /CN=RSA root CA
subject = /CN=RSA issuer CA

depth = 2
issuer = /CN=RSA root CA
subject = /CN=RSA root CA

depth = 0
issuer = /CN=EC issuer CA
subject = /CN=mx1.example.com

depth = 1
issuer = /CN=EC root CA
subject = /CN=EC issuer CA

depth = 2
issuer = /CN=EC root CA
subject = /CN=EC root CA