I'm doing that now. Have had the free account sitting around for a while now. Decided to upgrade to the $5 version of mail before really starting to use it. They STILL endlessly blast you with that self-promotion. Full-page ads, at that. I'm immediately having regrets about my decision to switch. I'll be primarily using Thunderbird on desktop, and on Mobile if/when they get around to the k-9 to Thunderbird switch, so I don't get their self promo there. But the behavior in general doesn't bode well.