E-mail scanning stops when using gmail account configured in Outlook as IMAP

Question

Hi, 
 SFV4C6 (SFOS 16.05.3 MR-3) 
 we are using Gmail ( Google Apps Legacy ) in Outlook configured as IMAP, and we are using e-mail scanning rules:

After some time Outlook just stops receiving e-mail and cannot connect any more. If I disable this scanning rule, then everything works again, but without e-mail scanning. If I reboot the SophosXG appliance, e-mail scanning works again, for some time. 
 This problem is driving us crazy. In latest FW, I saw something was repaired for POP/IMAP ( certificates issue ), but it seems that our problem persisted. 
 I have not regenerated appliance certificates after upgrade form v15. 
 Any clue anyone ? 
 Thx.

XGFirewall User · Answer

I was experimenting with many options. Finally following trick worked. 
 
 This is not related to Email Scanning Policy. 
 I was using "Block high risk (Risk Level 4 and 5) apps" Application Filter in User/Network profiles, and that Application Filter policy is blocking "GeeMail Website" application. That was blocking google imap/smtp also. 
 Therefore I have modified default "Block high risk (Risk Level 4 and 5) apps" policy. Added "GeeMail Website" application on top, Action=Allow and save.