MSN Messenger and Hotmail users will soon have access to a mobile version of those services.
Openwave Systems has integrated clients for Microsoft's instant messaging and web-based e-mail services into Phone Suite V7, the latest version of its application software platform for GSM phones.
Hotmail users typically read and reply to their mail online, a costly business when paying by the second for mobile internet access.
However, the mobile client can work online or offline, said Phil Holden, Microsoft's director of MSN international subscriptions at the 3GSM World Congress in Cannes.
Likewise, where MSN Messenger's presence indication shows users as "offline" if their fixed network connection drops, it will show mobile users as "connected" long after their phone's data connection has dropped.
The server can still deliver messages to the phone via GSM's SMS, he said.
In addition, Openwave's V7 software can be configured to remember users' Microsoft Passport identities and automatically log them in each time the phone is turned on.
The MSN Messenger service carries around 75 billion instant messages a month, mostly from users connected to fixed networks. That is almost double the number of SMS messages carried by the world's GSM operators.
Fixed-line internet access is available for around €1 an hour in many European countries, or for a fixed monthly fee, making online chat using a PC relatively inexpensive.
Mobile users, on the other hand, pay between €0.05 and €0.50 to send an SMS of up to 160 characters, and mobile internet access may cost up to €10 an hour.
Microsoft is discussing different pricing models with network operators, to bring down the cost of using the mobile MSN service.
The Openwave-MSN software will appear later this year in phones from Sagem and two other European phone manufacturers.
Sagem developed its phone, the SG321i, for a particular network operator, and is awaiting approval from the client before releasing the phone.
Peter Sayer writes for IDG News Service