Personally, I'm skeptical. Just because it worked for him doesn't mean it's a general solution. Many people have experienced exactly the opposite behavior from spammers: they try the lower priority MX records first, or they ignore the MX priorities entirely.
I put this in the same category as many other so-called "solutions" to the spam problem. They're temporary hacks which will only work so long as they don't gain critical mass, otherwise spammers will adapt. And once spammers quit exhibiting the particular behaviors these tactics target, these tactics will fail completely because they have no ability to adapt to new spamming behavior. Contrast this with, for example, robust content filters such as Brightmail and IronPort Anti-Spam, which are able to adapt as spammers change their content tactics.
Another one that annoys me is the idea of using a long delay before responding to the EHLO or before giving the banner, and dropping client that jump the gun and respond before the banner or the EHLO response.
It's a pain to debug a SMTP problem when you have to wait 30 seconds or more for a hello banner to respond after to connection is open. It's just another so called "solution" to stopping spammers.
In my opinion SMTP CallBacks fall into this group of spam kludges also.
DocumentationCode download linksGoalRequirementLimitationsSupported ISR
and UCS-E ModelSupported ISRG2 and UCS-E Blades:Supported ISR4K and
UCS-E Blades:Step by Step ConfigurationConfigure one of the connectivity
options to access the Cisco IMC from the n...
Firepower Threat Defense (NGFWv) on UCS E-series - Transparent Mode in
HA DocumentationCode download linksGoalRequirementLimitationsSupported
ISR and UCS-E ModelSupported ISRG2 and UCS-E Blades:Supported ISR4K and
UCS-E Blades:Step by Step ConfigurationCo...
Question I am currently unable to specify "crypto keyring" command when
configuring VPN connection on my cisco 2901 router. The following
licenses have been activated on my router :