V3 extensions allow more configuration options to be inserted in the Code Signing Request, such as alternative subject names and usage restrictions to certificates.
To add one or more Subject Alternative Names, enter the same information that would go in the extensions section of an OpenSSL configuration file. For example:
TEXT
[ req ]
req_extensions = v3_req
[ v3_req ]
# Extensions to add to a certificate request
subjectAltName = @alt_names
[ alt_names ]
DNS.1 = server1.example.com
DNS.2 = mail.example.com
DNS.3 = www.example.com
DNS.4 = www.sub.example.com
DNS.5 = mx.example.com
DNS.6 = support.example.com