phenomlab yes, it's a long story we used to rely on zfast.co.uk but they do change their IP always :/ and i had to update the same ip in Cloudflare.
zfast email server
It's a bit complicated configuration and i don't want to keep tracking it, two days ago switch to elastic email for outgoing (for flarum and other signups only) and Rackspace (for regular conversation using smtp) 1 mailbox is $1 / month. in rackspace they have a feature to capture all emails and forwarding them to my Gmail box.
but, i am linking this ❤ less stress-free configuration.