I lost faith in iCloud custom domains a few months ago, I was receiving the usual marketing emails etc fine, but actual person to person emails? Sometimes repli

I lost faith in iCloud custom domains a few months ago, I was receiving the usual marketing emails etc fine, but actual person to person emails? Sometimes replies would come through, other times nothing. I thought at first people were just ignoring me, but when a company reached out to me over SMS to respond to a complaint I had, they said their email reply had bounced so was contacting me on SMS instead Switched to fastmail at that point.