Offer your best promotions and get to the point, already -- or customers will unsubscribe just as quickly as they opted in to receive your instant messages.

ICQ, a once-popular instant messaging service, announced on Friday via its website that it would be shutting down next month. "ICQ will stop working from June 26," reads a message on ICQ.com.

Exchanging text messages in real time between two or more people logged into an instant messaging (IM) service. Unlike email, messages are sent immediately, whereas email can be queued up in a ...