This client sends me too many emails, halp I'm getting stressed and depressed


You are wrong! It means you're not sending enough emails. Emails go BRRRRRRRRRR when client prefers emails because client is unaware and unwilling to try other options.
Client eventually can't keep up and goes: "I'm sorry for responding late...."
You go: "Hey I send you an email the other day if you could respond this week, you might've missed it so I'm just sending you a friendly reminder otherwise you won't make your deadline

"
Client goes: "oops I think I missed another email"
You: "No problem, I'll resend it. In the meantime let's onboard you on Monday or another project management tool and we won't have to send so many emails anymore"
Client: "Oh wow, you are genius I can use this for other things too"