Trick for blocking email spam

Fake MX records can work like greylisting and often much faster. It doesn’t require the installation of new software. What you do is add a fake highest and lowest MX record. Normal email will probably retry but spammers often don’t. This is especially true of virus infected windows zombie spam. Here’s an example MX configuration.

please carefully read complete article: Spamassassin Other Tricks

some tips for this:

Simple way to check the MX-Records (and the other records of course) of a host should be:

host google.com

Response:

google.com has address 173.194.69.138
google.com has address 173.194.69.100
google.com has address 173.194.69.101
google.com has address 173.194.69.139
google.com has address 173.194.69.102
google.com has address 173.194.69.113
google.com has IPv6 address 2a00:1450:4008:c01::71
google.com mail is handled by 10 aspmx.l.google.com.
google.com mail is handled by 50 alt4.aspmx.l.google.com.
google.com mail is handled by 40 alt3.aspmx.l.google.com.
google.com mail is handled by 20 alt1.aspmx.l.google.com.
google.com mail is handled by 30 alt2.aspmx.l.google.com.

Now have a close look on the different mailservers (MX records).

The value after "by" is the so called priority of each entry.

Notice the point at the end of aspmx.l.google.com. and the other mailservers. This called root-label, which does not have a formal name and its label in the DNS hierarchy is an empty string.

Fully qualified domain name

More advanced way to check for records is nslookup:

nslookup  set type=MX  google.com

Response:

Server: 192.168.178.1 Address: 192.168.178.1#53

Non-authoritative answer: google.com mail exchanger = 40 alt3.aspmx.l.google.com. google.com mail exchanger = 20 alt1.aspmx.l.google.com. google.com mail exchanger = 50 alt4.aspmx.l.google.com. google.com mail exchanger = 30 alt2.aspmx.l.google.com. google.com mail exchanger = 10 aspmx.l.google.com.

Authoritative answers can be found from: alt1.aspmx.l.google.com internet address = 74.125.141.27 alt4.aspmx.l.google.com internet address = 74.125.137.27 alt2.aspmx.l.google.com internet address = 173.194.64.27 aspmx.l.google.com internet address = 173.194.69.27

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