Hotmail/Outlook (any Microsoft email services) folks. Microsoft is currently blocking our emails. We have raised a support ticket with them and will update when we can.
In the meantime it's possible that adding robot@evoweb.uk to your address book/contacts will help and if you're able to switch to a different email provider, that would work fine.
We have also increased the number of bounce emails we can handle before accounts are marked as requiring verification again to hopefully mitigate the issue a bit as well.