Relatives of the 19 elderly people who died inside Orchard View care home in Copthorne, West Sussex, told an inquest into their deaths they were concerned about the levels of care inside the home.
Call bells were often not answered for long periods of time, and in some cases were in places that the residents could not reach.
Relatives said their loved ones were not tended to properly, were often left unattended and physically inactive for long periods of time, and were not given any mental stimulation or attention by staff.
More top news
The Information Commissioner’s Office said BT did not have customers’ consent to send the emails.
The 23-year-old was held on suspicion of doing an act likely to cause an explosion to injure or damage property, and endangering safety.
Three men died on the track between Brixton and Denmark Hill in south London.