If some users on a server have a very long list of whitelist and/or blacklist entries, it will
slow down mail processing for everyone on the server. On a server with
moderate to high levels of email going through it, this could cause a
noticeable slowdown in mail delivery and possibly other processes on the
server such as web page loading times. Every mail has to be filtered
against every user's whitelist and blacklist entries, plus all the other
spam rules, attachment checking, and virus checking. This takes up
memory and CPU time and slows down the processing of email and
potentially slows down the server. This is why it is important not to unnecessarily
add to the time required to check each mail.
Whitelisting and blacklisting should not be done on a blanket basis.
It's not necessary. It's not like boxtrapper where a sender has to be on
the list in order for their mail to get through to you.
There are actually very few legitimate situations where it is
necessary to whitelist an email address. Some examples: An
Internet-based company (like a domain registrar or online store) whose
emails may occasionally get tagged as spam because of images, etc., but
you need to ensure that you receive them, or a non-spammer whose ISP's
IP address is on an RBL (spamming black list) and thus their email is
marked as high scoring spam.
If you are getting spam false positives, you should raise your spam
scoring threshold (high and low scoring spam score levels) or take other
action to fix the false positives instead of putting a lot of people on
their whitelist. See this FAQ
for more information on correcting false positives, and this FAQ
on teaching the SpamAssassin Bayes filter about what is spam and what
is not spam. We recommend leaving both low and high scoring spam set to
be delivered rather than deleted for a while until you are sure that
their scoring thresholds are okay and email you want to receive is not
getting marked as spam.
If you really want to raise the limit on the number of blacklist or
whitelist entries, go to WHM > ConfigServer MailScanner FE >
MailScanner Front-End and modify the value for Maximum entries per
account in their blacklist and/or Maximum entries per account in their