Ethically he should have as others said at least told you in a session and given you a couple weeks to figure out the next step. Him offering this "final goodbye" is a small step in the ethical direction but he should have done more. IMO its the cowards way to terminate over email unless you are the client doing the terminating.

I am very sorry you are going through all of this. Its so hard not only to end with a therapist but also to realize how much power they have when it comes to terminating. I had a therapist who took a leave of absence and disappeared so there was no final session or closure and its been ROUGH trying to move on and grieve. Others have given me notice and that final session gave me enough closure to move on faster and better. I am not sure if you are someone who needs closure or if its important to you but if it is I would make that the goal for this session he is providing. Once a therapist makes up there mind to terminate, that is what happens unfortunately. I have never had a therapist change there mind about termination. Maybe use this time to talk about your work together and what you accomplished with him and maybe get some referrals if that is what you want. Its a very hard thing not only to feel but to face head on. It won't be easy but it can be worth it. You have this chance now to see him one last time and say whatever needs to be said. I would give anything to have had that with my last therapist. I wish you the best of luck and keep posting here if it helps you.