Last Tuesday, NTT Docomo’s SP-Mode smartphone network infrastructure was hit by a congestion-related bug, causing a handset and mail address mismatch affecting tens of thousands of subscribers. When a mail was sent from an affected handset, it would appear to have been sent from an unknown address, and replies to these mails would get routed to the stranger's address, not the actual sender's.

Despite DoCoMo's earlier claims that at most 10,000 handsets were affected, the company reported today that the current count has reached 18,698 individuals. And while it claimed that the problems were almost entirely cleared up by the evening of the 20th, some SP-Mode services such as money transfers were suspended until noon on the 22nd so that transmission equipment could be inspected.

The company is doing its best to contain the damage in the privacy-sensitive country: on top of offering newspaper and direct mail apologies, DoCoMo has appointed its president to a team to make sure the incident doesn't get repeated, and it's announced plans to strengthen its server architecture and add a new verification mechanism to make sure handsets and IP addresses stay in sync.