tl;dr If you are sorting email messages from this server based on email headers, you might need to update your filters.
This list has been moved from one server to another server.
Previous List-Id header was sigsum-general.lists.sigsum.org Current List-Id header carries more cruft but the regular expression sigsum-general.lists.sigsum.org should still match.
Previous Subject header was pre-pended with [sigsum-general]. Current Subject header might have changes in casing.
Previous server did not DKIM-sign outgoing messages which was problematic since the list manager rewrites parts of the message (like Subject), rendering potential present signatures invalid. Current server does DKIM-sign outgoing messages.
Previous list manager did not ever rewrite the From: header, making SPF checks at the recipient's server fail. Current server rewrites From: when needed.
Previous list manager had no web interface for managing subscriptions. Current list manager does.
Previous list manager accepted email messages to sigsum-general+subscribe@, sigsum-general+unsubscribe@ and sigsum-general+help@. Current list manager accepts messages to other addresses, see the List-* headers of any email received on the list.