We got this error when we tried to run sa-compile to compile the rulesets in SpamAssassin:

#  sa-compile
[30917] info: config: failed to parse line, skipping, in ".../local.cf": check_mx_attempts 1
netset: cannot include 127/8 as it has already been included
......
sa-compile: not compiling; 'spamassassin --lint' check failed!

Running "spamassassin --lint" directly got the same error:

# spamassassin --lint
[30607] warn: config: failed to parse line, skipping, in ".../local.cf": check_mx_attempts 1
[30607] warn: netset: cannot include 127/8 as it has already been included
[30607] warn: lint: 1 issues detected, please rerun with debug enabled for more information

Then we edited the file "local.cf", and commented out the line for "check_mx_attempts 1", then sa-compile was happy.

So we looked around, and found the answer:

We are using SpamAssassin 3.2.x. The directive "check_mx_attempts" is no longer valid since SpamAssassin 3.0.0.