Trillian

Trillian is an universal instant messaging client developed by Cerulean Studios and will allow you to connect to all your IM : Trillian (formerly Trillian Astra), Google Talk, Jabber, Yahoo !, Facebook, Skype, ...

In addition to connect to your various instant messaging with a single program, you can also add simple email accounts (POP3 and IMAP). With this additional support, Trillian will be able to notify you when you receive an email on your e-mail address.
Note that it's preferable to use IMAP, because the default configuration of POP3 is to deleted mails from the server (this isn't a choice of Cerulean Studio, but the POP3 standard that was intended by default).

Warning: Microsoft has put all MSN servers offline.
So, Trillian (and official MSN clients) don't allow anymore to connect to the MSN network.
But, you can add your Hotmail account with the IMAP protocol using these informations :

• address : imap-mail.outlook.com
• port : 993
• SSL : enabled