Authentication are only necessary when using personal accounts outside the domains of Tornevall Networks.
It is still possible to get whitelisted here, so no authentication are needed. However, this is limited to static connections, with IP-addresses that are never changed by your ISP.
Examples on non static addresses are such hosts that are delivered by Telia, Tele2, Telenor, etc.

The authentication is always the credentials you are using to read and write mail via tornevall.net