If the backup mx server (backupmail.xyz.com) is no longer in service, but the mx records stay the same as below:
10 mailserver.abc.com 104.x.x.x
20 backupmail.xyz.com 104.x.x.x
What happens if the primary mx goes down? What will be the experience? Will it have a bounced email? What options do I have to prevent this from happening?