Mail Filter Settings, explain please.

[Robert Baldwin]

What do these settings actually do? I am unable to determine this from 
the description.

Check messages for mismatching From header and envelope from :
enabled: kolabfilter-verify-from-header: TRUE
disabed: kolabfilter-verify-from-header: FALSE

Use the Sender header instead of From for the above checks if Sender is 
present :
enabled: kolabfilter-allow-sender-header: TRUE
disabled: kolabfilter-allow-sender-header: FALSE

Action to take for messages that fail the check: :
Reject the message, except if it originates from the outside and the 
 From header matches one of Kolab server's domains. In that case rewrite 
the From header so the recipient can see the potential forgery.
selected: kolabfilter-reject-forged-from-header: FALSE

Always reject the message. Note that enabling this setting will make the 
server reject any mail with non-matching sender and From header if the 
sender is an account on this server. This is known to cause trouble for 
example with mailinglists.
selected: kolabfilter-reject-forged-from-header: TRUE