Debug
Not for use by normal users. Setting this option to "yes" will put MailScanner into debugging mode, in which it creates slightly more output and will not become a daemon.
Always Looked Up Last
This option is intended for people who want to log more information about messages than what is put in syslog. It is intended to be used with a Custom Function which has the side-effect of logging information, perhaps to an SQL database, or any other processing you want to do after each message is processed.
Its value is completely ignored, it is purely there to have side effects.
If you want to use it, read CustomConfig.pm.
Deliver In Background
When attempting delivery of any messages (when the "Delivery Method = batch") the sendmail/Exim command will be run in the background so that MailScanner does not have to wait for the delivery attempt to complete. There are very few good reasons for setting this to "no".
Delivery Method
With this option set to "batch", then an attempt is made to deliver all of the messages in the current batch once they have been completely processed by MailScanner. With this option set to "queue", the messages are just placed in the outgoing queue, leaving sendmail/Exim to attempt to deliver them the next time it processes its queue. This can be useful on servers with very high load.
Split Exim Spool
Are you using Exim with split spool directories? If you don't understand this, the answer is probably "no". Refer to the Exim documentation for more information about split spool directories.
Lockfile Dir
This is the directory in which lock files are placed to stop the virus scanners used while they are in the middle of updating themselves with new virus definitions. If you change this at all, you will need to edit the "autoupdate" scripts for all your virus scanners.
Lock Type
Do not set this option to anything unless you know exactly what you are doing. For sendmail and Exim, MailScanner will choose the correct value by default. This affects how mail queue files are locked, and your mail will be totally screwed up if you set this option to anything other than the correct value for your MTA. So leave it alone and let MailScanner choose the correct value for you.
Minimum Code Status
Some of the virus scanners are not supported by the authors of MailScanner, and they may use code contributed by another user. If this option is set to the wrong value for your virus scanners, then you will get an error message in your maillog (syslog) telling you that it is set wrong and MailScanner will refuse to start. The error message will include the location of a web page describing this option in more detail, and this tells you what value to set this to for each virus scanner that can be used by MailScanner.