If you are using a Sonicwall Firewall, you will need to ensure that no policies exist to prevent certain IMAP commands. In the screenshot below you can see that items 13 through 16 are specifically for Ipswitch IMAP functionality. These policies were intended to prevent vulnerabilities in older versions of IMail. The current version of IMail no longer has these issues. To correct the problem, disable or remove these Sonicwall policies.