Is there a way, feature or a modification that allows to send emails to an entire member group at once? 

didnt find anything in the marketplace 

ACP -> Members-> Bulk Mail.

You can already do this with the native bulk mail feature

Ah ok, thanks

I'm trying to set up a discussion forum. I would like all members of the forum to be notified by email when a new topic is created. Is there a way to do that?

8 minutes ago, Frank Casper said:

I'm trying to set up a discussion forum. I would like all members of the forum to be notified by email when a new topic is created. Is there a way to do that?

You have to make members follow the forum. 

- For existing members:

- For new members: