I have. As I have two mail accounts with the same provider and only one has problems, Apple cannot say that the solution must come from the provider.
On the phone I was told that they are working in it. Should I believe them? But Even if I do not believe them, I have no other way than using another app and waiting.
I strongly believe that we need, all of us, to contact them. The more complains they have, the better for us. But we must not accept that they say that it is our or the provider’s mistake. We all have a tablet where our mail functions. We can all bring at least this as argument. It is not also very logical that so many mail accounts have problems just by updating the IOS. So if they tell you that it is the provider’s problem, it is up to you (to your arguments and your patience) to tell and insist that this is not the case and make them accept it.
I think that the issue has not yet reached the ‘press’. That would help us a lot, I think, as for the time being we are complaining between ourselves.