"Couldn't you just use the DNN event viewer?" yes I could, my description was not very accurate, the only thing I want to know for now is if a person has logged in and when.

The users would have to register "manually" and then receive the link by email.
The site I'm going to replace uses a custom ASP script now and I want to move it to DNN for obvious reasons.

Now the only thing the user needs(after registration)  to "log in" is their email address, but I think it's a bit to simple.

I guess your right and I will have to create a custom module for this (not everything has already been developed by others....)

Thanks for your tips, by the way....:-)