[bitfolk] A part of me dies every time Hotmail junks my emails

Hi all, I'm having major issues with Hotmail/Outlook.com junking every single email (100% transactional) I send from my VPS ('Smartscreen blocked this email..') and is causing a headache in the form of customer complaints/support especially as the majority aren't technically inclined. I haven't had any issues whatsoever from any other major email providers and I only send a very low email volume (usually less than 500 emails a month in total). I've done everything I can think of to ensure I'm a reputable sender.. SPF/SenderID, DKIM and Reverse DNS all validate perfectly. Mail server uses an appropriate HELO, my IP is sparkly clean and not on any blacklists. Signed up to Hotmail complaints feedback loop, smart network data services, went through an automatic mitigation procedure which was apparently successful. The emails I send are mostly just plaintext alerts/receipts so there isn't really much I can do to make them look less 'spammy' and more 'hammy'. I'm still dealing with Hotmail directly to find out what the problem is, but I was just wondering if anyone might have any suggestions? Have you experienced this? Perhaps I should just give up and relay mail via a high reputation ISP such as Amazon SES or something.. Cheers, Luke