... Funny thing is that I use gmail and their own promotional mail got into the spam folder!
For years I thought Windows is the worst product on this planet. In 2005, I switched when I realized that my day starts not with my computer serving my needs, but me serving the computer: download and install latest virus definitions, check for malware, etc.
Now my day starts with checking what Gmail erroneously sent to the spam folder. Without exception, 99% of my Linked In communication is already there (one way for Google to deal with the competition, I guess). And, as you noticed, Google's own product ended up in their spam folder too. How ironic.
I simply stopped using Gmail for anything serious and important.