Yeah, that's my primary concern, but as I said, I have trust issues with third-party services holding stuff like my contacts lists and content, having lost data and functionality to service shutdowns on at least three occasions.
I already run a dovecot/postfix mail server that handles stuff like sending out client invoices, so I was thinking I could slap mailman on there, as I've already smoothed out issues with recipients using Gmail and Outlook.
I suppose an ideal option would be a service that could take an RSS feed and just email it to people, although it would still mean entrusting a subscription system to a third party.
I've run Mailchimp for other people before, and I'm not a fan.
I do like Google Groups for this (again, something I run run for someone else), but having deGoogled myself a couple of years ago, I don't want to go back down that path (especially as Google was responsible for one of the aforementioned data loss incidents).