Expected Behaviour:
Users shall be able to download attachments from gmail web interface, once the are allowed to go to gmail web interface. After attempting to whitelist all known google domain names, I would expect that I get either some error or log entry in pihole with [piholed] status, but I see nothing I would be able to fix.
Actual Behaviour:
while users log in to gmail (G-suite) in browsers (Firefox, Chrome, IE - all latest version on Win2012 r2), they can not download any attachments, the download link on any kind of attachment (pdf, jpg, doc, xls,...) does simply nothing. No error, no attempt, nothing.
The fix is to disable for a short period the pihole service and re-enable tit again or to run the pihole -r command, then it wors for all users for a day or half or so. Not sure what the cause can be.
whitelisted:
googleapis.com
googleusercontent.com
Debug Token:
Your debug token is: 3tnd6bja84
Did anyone experience teh same issue? Can it be prevented somehow?
I can only think of cron job restarting pihole every hour or so 
but that is not a solution...
Update 5h later:
I have again started debugging the logs and tested one desperate solution. I saw somewhere that the attachments are served from host mail-attachment.googleusercontent.com. While I had a whitelisted host googleusercontent.com I would say it also includes the early one, but I added that one too to whitelist. Before I did that, the attachments didn't work again and now they seem to work. Not sure, whether it is only a side effect of updating the whitelist and whether it keeps working also tomorrow, I will see. Will update here once I get this confirmed.