Can't send with Email Pro from iPhone

I'm following the guide provided by OVH to configure the email pro service on the iPhone, step by step, it just doesn't send emails, I can receive, but not send. I readded the configuration times and times over, everything is meticolously correct exactly like the guide, and yet, it doesn't work, anybody has an idea why wouldnt it send from the iPhone while the web client works? (it's not a SPF record domain problem, the respective records are there).

It seems absurd to me that you pay for a service to be provided with you, and it's almost implied that the service is gonna be used on third party clients, and OVH doesn't care in the slightest to give you support even when **their own** guide doesn't work. At the moment I just wasted my money and I cannot use the service as I intended to.