Craig Sanders wrote: [backscatter hellhole snipped]
note that spammers and viruses STILL target secondary/backup MX servers....and 99.9999% of the time your customers only THINK they need a backup MX (mostly because they're relying on obsolete advice from over a decade ago when backup MX servers weren't such a bad idea). these days they are rarely needed, and generally cause a lot more trouble than they are worth.
I'd be curious as to any details on how things had changed in the past 10 years.
What is listed in our DNS as a backup MX is currently not accepting smtp connections, as we don't have recipient maps or any spam filtering there and this causes problems....
On our TODOs list is getting spam/virus protection on the backup MX.