Missing all incoming email messages from 3/21/2019 thru 4/12/2020

A large block of my inbox email messages disappeared for the period   from 3/21/2019 thru 4/12/2020.   I was moving messages in my online comcast email into separate folders by year when this happened.   All of a sudden my computer seemed to crash and then I discovered that this large block of email messages were missing.   They weren't in trash or deleted folders or anywhere else online or on my computer.     Are these backed up by Comcast somewhere so that they can be retrieved?