For some inexplicable reason, Smartsheet is blocking the domain name protonmail.com. According to Smartsheet Support:
"Upon checking our documentation as of 1/25/2021, we have confirmed with the product team that protonmail.com is blocked by design. With that being said, users with a protonmail.com email address, will not receive automated emails from Smartsheet. This includes automation, share sheet, at_mention, sign-up confirmation, password resets, and more."
Why would Smartsheet block users of an e-mail service from creating a Smartsheet account and utilizing Smartsheet services? Why does Smartsheet care what e-mail service its customers use?
Stop discriminating against Proton Mail users and give them access to Smartsheet!