Hooray!
What is generally recommended is that your forum run on a subdomain (e.g., www.example.com, forum.example.com). Then you’d be using xxx@www.example.com as your mail domain and not have an issue with receiving mail at example.com. So then you would configure incoming group/category posts as whatever@forum.example.com. (And it’s really best to not run your web site on the naked/apex domain: Ojktoto > Ada Togel Online Terbaik Di Situs Toto Terpercaya)