I want to subscribe to a Proton Mail Premium plan when there's a good discount. My goal is to use the custom domain feature so I can use my own domain instead of proton.me. This looks more professional and also obscures the fact that I'm using Proton's infrastructure. My question is, if my subscription expires, will I still be able to receive emails? I'm concerned about this because I want to use it for academic work and publishing my papers, and I want it to remain active for years. However, I'm worried that if I can't renew my subscription, my emails will become inaccessible. What's your opinion on this?