How to resolve primary virus scanner (auto) error in Mailscanner

You may find you get an error like:

Unable to select a regular expression for your primary virus scanner (auto) – please see the examples in functions.php to create one.

This happens when you are using newer versions of MailScanner and have the auto setting turned on in your MailScanner.conf file. Edit the configuration and set the string for your virus scanner instead of using the auto setting like:

##Virus Scanners = auto
Virus Scanners = clamav