Microsoft and Yahoo will make their respective consumer instant-message (IM) networks partly interoperable in the second quarter of next year, the companies announced Wednesday.

However, communications between MSN Messenger and Yahoo Messenger users will be limited to exchanging text messages, PC-to-PC voice chatting, sharing some emoticons and adding contacts from both services to their contacts list, said Dan Rosensweig, Yahoo's chief operating officer.

"We're thrilled to be talking to you about interoperability between Yahoo Messenger and MSN Messenger," he said.

275m users slappin' smilies

Combined, MSN Messenger and Yahoo Messenger will have an estimated 275 million users, according to the companies. However, AOL's AIM service is the single largest IM network in terms of users.

AOL AIM interoperates with other IM platforms, such as Apple's iChat, Reuters Group's system and AOL's own ICQ, a sister IM network to AIM.

Like the Yahoo and Microsoft plan, the interoperability tie-ups that exist in the industry between different services are invariably limited to a set of features, as opposed to full interoperability.

Microsoft's security promise

In the case of Yahoo Messenger and MSN Messenger, the companies decided to focus on key core features, such as text messaging and PC-to-PC voice communications, and, at least for now, leave out advanced features such as games and photo sharing, Yahoo and Microsoft executives said.

They also stressed repeatedly that the hard work for the Yahoo Messenger and MSN Messenger teams begins now, because linking the two massive IM networks will be complicated, particularly since both companies want to make sure users' security and privacy aren't compromised in any way.

"This is one of those situations where one-plus-one can equal three," said Blake Irving, corporate vice president of the MSN Communication Services and Member Platform group. "We're excited to announce plans around something that we know for a fact will delight our users."


The news may mark a move against Google, which is positioning itself as a strong challenger with its Gmail Web mail service and new Google Talk IM service, Delaney said.

"I think Google represents a big threat both to MSN and Yahoo, both of whom are based on communication services," Delaney said.

Jeremy Kirk in London contributed to this story.