Gmail uses multiple Google owned domains, not just gmail.com and such. Check your blocked domains stats to find them out.
Further hints will be offered by a simple forum search too. When I last checked three years ago for related domains, I got these results. This may have changed in the meantime. You'll have to find it out.
"white list does no work"
It does work if you fill it with the correct values. And fill it only with domains which are actually blocked by your settings, else you're wasting your 25 whitelist entries for nothing, exactly as you have experienced with your current whitelist assumptions "gmail.com, mail.gmail.com". Especially the second is already obsolete, because the first covers already gmail.com and all its subdomains. And the most funny thing is that mail.gmail.com even does not exist. So using it does neither block nor allow it. A clear sign that you have had no ideas stumbling in the dark. This has hopefully changed now.
