ClamAV will function without any issues, as the built-in product is designed to work with within the parameters of the SmarterMail file locking system.

 

The general rule of thumb for any external antivirus package is that it should be excluded from directly accessing any portion of any SmarterMail file - period.  The reason behind this is that SmarterMail's processing of data is extremely fast and allowing any external program to access the data could cause a simultaneous lock on a file, causing corruption to message data, usernames, passwords, SmarterMail configuration, and other aspects of the program.

Having said that, you can still use an external antivirus program, but you must call the program from within the SmarterMail antivirus command line parameters:

 

You can also enable QUARANTINE any messages found to contain viruses, if you enable that option in AV options.

Go to Antivirus Administration, as the SmarterMail Admin, and then click on ONLINE HELP, and you will get a description of all of the options and how they work.