A conversation no as Jake says. But I guess what you're after is reachout - a conversation would kick off a notification email so it would reach out to them and invite them to come and see.
You could do this by sending them an email by usergroup.
admin/ Users tab/
Email users (sidememu)
It depends how you set up your usergroups. The recommended way is to use Registered for all active users (not banned, not heavily restricted, left)
Then you can select Registered for this.
If you did not do that -and you might consider changing if you did not - you could select your key usergroups for this message.
However be advised this type of email does not get stored
So copy paste it into a document in your site tracker folder on your computer. Forgive if this is something you already know, but it's well worth it to keep a kind of site diary here, noting the key changes you make esp. code alterations.
Thanks for you answers. When my forum is migrated I will send all registered users an e-mail with all necessary information to gain access to the new platform. My intention with the conversation mail was to welcome the users in a another way and at the same time point out some usefule resources to get the most out of the new platform. I will do some more research of the database and see if I can figure out how the messages are stored. Maybe I can come up with something there.
I'm a little bit tired. I just realized that I'm using NUNS But ONLY for new users registering with the forum. I would like to be able to use basically the same function NUNS is relying on, but for all users when they are migrated to the new platform.