Finding out the best Ubuntu MSN, two Linux Messenger MSN are found, which will be great for you to run as your Ubuntu Messenger. The MSN Ubuntu can be found in the following links, for your MSN Linux download:

Emesene

Emesene, which can be read as eM eS eNe ( M S N ) is one of the best software I found as alternative to MSN for Windows.
Check out the following link for details:
http://www.webtechquery.com/index.php/2010/04/msn-messenger-linux-ubuntu-debian-fedora/

aMSN

aMSN is another good alternative to MSN for Windows. To check out details for aMSN, check out the following link:
http://www.webtechquery.com/index.php/2010/03/msn-messenger-for-linux-ubuntu-fedora-etc/

Hope this will help you installing your Linux Messenger MSN