Charter Communications officials believe a software error during routine maintenance caused the company to delete the contents of 14,000 customer e-mail accounts.
There is no way to retrieve the messages, photos and other attachments that were erased from inboxes and archive folders across the country on Monday, said Anita Lamont, a spokeswoman for the suburban St. Louis-based company.
"We really are sincerely sorry for having had this happen and do apologize to all those folks who were affected by the error," Lamont said Thursday when the company announced the gaffe.
Charter, one of the nation's largest cable TV operators, also provides telephone and high-speed Internet service.
It has applied a $50 credit to the bill of each customer whose account was affected by the mistake, Lamont said.
Charter gives each new Internet user a free e-mail account, but some customers opt to use other accounts instead.
So every three months the company deletes inactive accounts, Lamont said.
"During this maintenance we erroneously deleted active accounts along with the others," Lamont said. "It's never happened before. They are taking steps to make sure it never happens again."
Charter provides service in 29 states, and Lamont said the affected customers were scattered around the country.
All told, the company has about 2.6 million high-speed Internet subscribers.
Computer experts advise backing up all important e-mail.