While I also pine for the simpler days when you could just make a mailing list out of a mail alias, the reality today is that there are a lot of facilities built to deter spammers that create a roadblock for legitimate email admins to work through. The main ones we are dealing with here are meant to deter email forgery. This happens when a spammer forges your email as the purported source of their abuse. Thus, the better email servers all implement features like DKIM, DMARC, and SPF, which are meant to stop such forgery. The problem is that when a mailing list server relays your message, it is seen as the forger. So, there is significant mangling of headers that has to go on for a mailing list to operate properly today. The admin is working through this.