Kevin Rosenberg

A backup MX host is a backup mail server. It will handle mail for a domain if the primary server is unavailable. It's been a useful feature for email reliablility.

It appears now that backup MX hosting in no longer an option due to actions of spammers. I've recently had to delete my backup MX host because a constant and rapid flow of spam messages has overloaded the server twice. I've had over 500,000 spam messages in /var/spool/mqueue waiting to be bounced back as invalid email addresses.

The ISP where I co-locate my server told me that this attack on backup MX hosts is common and they actively recommend not using backup MX hosts. In fact, for their many thousands of customers, they no longer use a backup MX host for their domain.

It's too bad that spammers have made this useful tool for email reliability now an impractical option. For now, such barrages have been focused on backup MX hosts. I wonder if it's just a matter of time before they move such attacks to primary MX hosts.

There's a similarity to the biologic host/parasite relationship. A parasite uses enough of the hosts resources to reproduce. But, if the parasite is so virulent that the host dies, the parasite is some what less effective because it no longer has the carrier. Perhaps the spammers realize if they take down primary MX hosts like they have taken down backup MX hosts, then there won't be any email at all for them to take parasitically abuse.

Fondly remembered, RIP our backup MX hosts.