Radiusauth authenticates against a radius server, it suffers from one problem, as radius servers do not suppport user lookups without a valid password it's impossible for dmail to know a user is valid until the user has first checked/read their email, when this occurs radiusauth stores the username for future reference.
To supply additional information (like groups=x.y.z or fwd=fred@domain) you can use the radius 'VENDOR-SPECFIC' attribute.
Define the host which is running your radius server, e.g.
radius_host x.x.x.x
Define the port which your radius server listens on, e.g.
radius_port 1812
(Old systems may use port 1645)
Define the shared secret, typically it's stored in /etc/raddb/clients, e.g.:
radius_secret testing
Define the attribute usually 26=Vendor-Specific for additional information to be returned typically defined in /etc/raddb/users for example:
DEFAULT Auth-Type = System Fall-Through = 1, Group-Name = "testing_group" , Callback-Number = "9,5551212", Vendor-Specific ="groups=adults,private"
e.g.
radius_attribute 26
Define a file to store radius users in (require for dmail), e.g.
radius_user_file d:\dmail\radusers.dat
radius_host 10.0.0.24 radius_port 1812 radius_secret testing radius_attribute 26
D:\dmail>type radiusauth.ini radius_host 10.0.0.24 radius_port 1812 radius_secret testing radius_attribute 26 radius_user_file d:\dmail\radusers.dat
D:\dmail>radiusauth.exe check bob mypassword +OK bob config 0 groups=adults,private quit
D:\dmail