SpamAssassin performance tips

[ISP List]

After much trial and error tonight, I have found the following entries in
my spam.assassin.prefs.conf file provide the fastest scanning performance:

# don't mess with mime encoded messages
defang_mime 0

# don't do dns based rbl lookups
skip_rbl_checks 1

# only check for a valid MX record once
check_mx_attempts 1

Turning on rbl checks can be expensive, but usually don't hurt too much (I
recommend running a local caching bind server on the same box that
MailScanner is on).

The big "slowdown" is the check_mx_attemps, by default it is set to 3
attempts with 5 seconds in between (!), which can mean extra long delays if
the domain being checked has a DNS server problem or doesn't have a valid
MX record.

Hope the above helps someone.

--Mike