I am managing a subscribed calendar through my iPhone and am curious about how iOS handles 4xx error responses from calendar APIs. Specifically, I would like to know if there is a process that stops the iPhone from attempting to sync the calendar if it consistently receives 4xx errors from the server. Does iOS have a mechanism to pause or stop calendar sync under such error conditions to prevent unnecessary data usage and battery drain? Any guidance or insights on this behavior would be greatly appreciated.

I have an online service where it lets people subscribe to iCalendar feed. I'm wondering if there is a way to force the subscriber (their Calendar client) to stop their subscription. I have some subscribers who subscribed to a feed that doesn't exist anymore. The annoying part is that these subscribers is fetching the data every 30 seconds! I looked at iCalendar specification and it doesn't look like this is supported. I tried few http response codes (404 and 410), but this doesn't stop the client. The user agent I'm seeing in the log shows "iOS/17.4 (21E219) dataaccessd/1.0". Any help is appreciated.