All emails are suddenly tagged as SPAM after a period of no problems with the antispam feature!

When this happens there must be a problem with your DNS configuration or one of the blacklist servers configured. POPcon PRO uses DNS to query these servers for the individual IP addresses found in incoming emails.

You can check DNS lookups to blacklist servers by using the PING command in a CMD window:

This command will check if the IP 192.168.1.1 is listed in bl.spamcop.net - the lookup should fail and not return an IP address:

C:\> ping 1.1.168.192.bl.spamcop.net

This command will check if the IP 127.0.0.2 is listed - most (but unfortunately not all) blacklists will list this IP for testing purposes - the lookup should work and the IP "127.0.0.2" is normally returned:

C:\> ping 2.0.0.127.bl.spamcop.net

If the first ping command does return an IP address something about your DNS setup is not correct - check routers, firewalls and use the IPCONFIG /ALL command to validate your network card setup.