Cablevision Systems Corp. (NYSE: CVC) confirmed Friday that it was working to fix "technical issues" impacting its Optimum Online email system.

Twitter was aflutter with dozens of posts from Cablevision customers claiming they were unable to access their Optimum Online email accounts, some for more than 24 hours. DSL Reports referenced the email outage Friday morning after Cablevision customers posted messages about it on its online forum.

The MSO, which counts about 3 million subscribers in New York, New Jersey, and Connecticut, released a brief statement about the outage Friday:

Cablevision, which also apologized for "inconvenience," didn't say when the outage began. It also didn't explain whether the outage was related to a software or hardware problem, or offer other details.

Comcast Corp. (Nasdaq: CMCSA, CMCSK)'s SmartZone email system went down last April, caused by a data center power problem that impaired some of the MSO's email servers.

Update: Cablevision issued a statement Friday afternoon that it had resolved the problem, identifying a "digital mail storage device malfunction" as the culprit.

"We believe that this was an extremely rare, one-time problem after more than a decade of uninterrupted email service and that no customer email was lost. We apologize to our customers and thank them for their patience," the company said, noting that the interruption started midday Thursday and that the problem affected a "minority of customers."

For subs that were hit, Cablevision said has ensured that no emails were lost.

— Steve Donohue, Special to Light Reading Cable