iCloud Mail

I have woken up to find my entire email inbox empty, is there any way to recover all these email’s as there were important emails going back years? I’ve checked the trash/bin folder and there is nothing in there, I’ve checked all the other folders to see if they had been moved into there and they are also empty, the only folder that has emails in is the “sent” folder. I have recently updated my iPhone I’m unsure if this has anything to do with it. Please can you help? Thanks