In April 2005 Microsoft announced a partnership with BlackBerry developer Research in Motion which would bring IM to corporate users of the popular device via LCS. But here are some links to simple software that allows the regular end-consumer like you and me to sign into your MSN Messenger account using your BlackBerry device.

Quick IM

QuickIM charges only a one time licence fee of $29.99, there is no annual subscription to pay. The software does not use costly text messages (SMS) nor WAP connections to connect to the MSN network. Most mobile messengers use WAP connections and do server polling every few seconds, which result into high GPRS data use and high data bill. As opposed to those solutions, QuickIM is very data bandwidth friendly, but requires a full Internet access GPRS APN (Access Point) instead of common WAP GPRS.

Works with BlackBerry as well as Symbian UIQ phones (SonyEricsson p800, p900, p910, Motorola A1000 …), PalmOS (Treo 600, Treo 650, Tungsten C …), Communicator Editions (9300, 9500, 7710 ...) and most J2ME MIDP 2.0 phones such as Series60 phones (Nokia, Siemens, Samsung, Sagem, Motorola, SonyEricsson …).

http://www.quickim.com/

eMSN

Chat with your friends and exchange photos made with your camera-mobile. This is all possible with eMSN, which comes for free* (ad-supported) and runs on almost all java-phones (including BlackBerry).

*Note that your mobile must be MIDP1 compliant and that you must have internet access on your mobile (eg. I-mode, WAP, or GPRS). The eMSN app comes for free, however it generates internet traffic. Therefore you have to pay your provider. In most cases using eMSN is cheaper than using SMS.

http://www.funrungames.com/emsn.php or over the air URLs:
http://www.funrungames.com/download/eMSN.jad for MIDP 2.0 devices. http://www.funrungames.com/download/eMSNLite.jad for MIDP 1.0 devices.