Forum OpenACS Q&A: lars-blog hostname in rss.xml file
Anyone know where the hostname for an RSS feed lives?
The SystemURL parameter in "Main Site" in site map seems to be what is read in this case. That explains why a grep -i -r host in the blog package didn't turn up anything :)
After changing SystemURL and going to the rss-support and regenerating the page (rss.xml), all was fine.