Marc is a Principal Solutions Architect helping customers solve complex problems with Open Source software from Red Hat. With over 20 years of experience in the fields of Linux, Security and Networking, Marc can successfully and knowledgeably help his customers.
Good catch! Yes, it should be your vendor.pem file catted/combined with the intermediate cert file.
$ cat vendor.pem gd_bundle-g2-g1.crt > mail.mydomain.pem