The Bowlr system sends out emails daily to the main club email address with a backup of the next day's diary.
The emails exist to ensure we've supplied a backup of the diary in case of an outage.
It's similar to how your bank will email you monthly or yearly statements without the option to unsubscribe. It's a system email rather than a marketing email and so cannot be disabled.
On virtually any email client or service it should take just minutes to set up a filter that will pick these emails up and put them in a folder out of sight. And that is currently the only option we recommend.