<proceed at your own risk>
In the past I have avoided a reboot by logging in to Smartermail admin > select Security > Antivirus Administration > uncheck "Enable ClamAV" > Save.
Next I use task manager to end task on clamd.exe.
Then I append PhishingScanURLs no to clamd.conf.
Once I recheck Enable ClamAV in the Smartermail Admin and click save I see Clamd.exe starts and my new configuration is working.
Please chime in if you feel there is a downside to this procedure.