To change the threshold you have to open the "spam" rule in your Account form. Choose "Message declared as spam..." from "5. Rule description" and enter the new value for the threshold.
This error message only occurs when a "real" JIT debugger like "vsjitdebugger.exe" from Visual Studio is installed.
It is never recommended to have such a JIT debugger running on a productive system!
The JIT debugger will attach to any process causing an unhandled exception and ask for debugging. So spamd.exe will be paused/blocked.
The error itself occurs deep inside of SpamAssassin and can't be avoided because of the port of SpamAssassin from Linux/Unix to windows.
The error does not influence SpamAssassin scans at all. So please de-register any JIT debugger from your system or exclude spamd.exe if possible.
For de-registering you need to clear the following registry entry:
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug] "Debugger"=""
on x64bit systems additionally:
[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug] "Debugger"=""
Addresses added by a SmartPOP2Exchange action are added to an auto-whitelist/blacklist, so these addresses are not listed in the Spam filter options. You can find the files for the auto-whitelist/blacklist under "%COMMONFILES%\JAM Software\SpamAssassin\etc\SpamAssassin\" (JAMAutoWL.cf or JAMAutoBL.cf)