No issues so far, though I’ve only had it for a couple weeks. From the sounds of it, they go above and beyond to make sure they stay off spam lists, going so far as to cancel accounts that are being used for marketing.

You do have a 300 outbound email limit per email account per hour, so that’s something to keep in mind. But I’d never butt up against that personally. But it could be an issue if you happen to get a lot of users, or someone decides to be a dick with “forgot my password” spam.