I trust you're doing well and staying healthy. I want to reach out to express my gratitude to you for always diligently responding to our emails over the past.

I am contacting you to share some news. Last week, there was a change in the point of contact.  As a result, A, who has been handling our communications until now, has stepped down from his role.
Moving forward, I'll be the one handling communications.  So, please feel free to reach out to me directly.  I would like to share emails with J, G, and B, who work together on our team. Is that okay?