Be careful when installing Yggdrasil Network on your device - your device address will be available in a network/peer explorers and if your firewall is not configured to reject incoming connections from the yggdrasil ipv6 interface - your locally running services could get exposed.
Should be noted that this does not apply if you install Yggmail only without mainline Yggdrasil, as Yggmail embeds its own node and does not use TUN.
this should be standard advise, always configure your host firewall correctly. Especially if you use something like ArchLinux where it doesn't come pre-configured