Thought I'd just add that I've setup critsend for sending normal mail notifications.

I also noticed that using http://mxtoolbox.com to lookup a domains MX can reveal the server IP (even through cloudflare), so to overcome this I searched around a little and found zoho.com
I'm using Zoho for sending custom mails from my domain and also able to receive them back, they offer a free package for 10accounts with 5GB per mailbox... all for free using your own custom domain! - https://www.zoho.com/mail/zohomail-pricing.html

As for the other methods I have performed edits on the upload files to disallow uploads from urls that could capture the IP by following this https://vborg.vbsupport.ru/showthread.php?t=313353

Anything else I should cover? :)