There is an incoming mail server installed on the server as described here.
See https://realtimevfx.com/admin/site_settings/category/all_results?filter=reply_by_email_address to see/change that. Anything that’s @mail.realtimevfx.com will work.
If you want to add post to group or category, you can do that, just choose email@example.com and it’ll just work.
One caveat: If you accept mail from those without accounts (if you turned on staged accounts), you’ll want to do create a gmail account and forward it, as there is NO SPAM FILTERING.