When the Exchange Information Store Service stops, what's impacted?

My company recently experienced an email outage that impacted a majority of our users. My exchange team is telling me they can't find a root cause, yet when I pulled the system logs I can see the Information Store service stop and restart itself 4 times over the same 10 minutes. They explained to me that the Information Store stopping and restarting would not have an impact on our users. However this seems contrary to the research I've done online.

So the question: What's impacted when the Information Store Service stops? Assuming no fail-over available.

Also, Once the service is re-started, how long does it take for email service to restore? The end user saw a 15-25 minute disruption in service.

Thanks for any help!

They're either woefully unqualified to administer Exchange or they're blatantly lying to you. Would users be affected? Undoubtedly. Here's the description of the Microsoft Exchange Information Store service:

Manages the Microsoft Exchange Information Store. This includes mailbox databases and public folder databases. If this service is stopped, mailbox databases and public folder databases on this computer are unavailable. If this service is disabled, any services that explicitly depends on it will fail to start.