Shuouma has released his dcGmail script for DreamPi which will enable you to use Gmail accounts with the Dreamcast. Not only will you be able to send and receive emails via the Dreamcast web browser but you'll also be able to play Sega Swirl's E-Mail Challenge mode! Simply follow the instructions below and Swirl away!
Instructions are here: https://dreamcastlive.net/sega-swirl-guide/