Hostname or e-mail is fine. Both are just a string. You can match it on your ER side.
The config with x509 looks something like this
site-to-site {
peer peer1.mydomain.com {
authentication {
mode x509
remote-id CN=peer1.mydomain.com
x509 {
ca-cert-file /config/auth/ca.mydomain.com.crt
cert-file /config/auth/dev.mydomain.com.crt
key {
file /config/ipsec.d/rsa-keys/localhost.key
}
}
}
connection-type initiate
description PEER1
ike-group FOO0
ikev2-reauth inherit
local-address any
tunnel 1 {
allow-nat-networks disable
allow-public-networks disable
esp-group FOO1
local {
prefix 192.168.33.0/24
}
remote {
prefix 192.168.70.0/24
}
}
}