Mail in spam

[Qwalk]

Some of my mails I'm sending to hotmail accounts, are being received in the JUNK folder.

Example of mail that goes into Junk folder:
Subject: Test
Mail body: Test

Example of mail that goes into Junk folder:
Subject: asdsdaasd
Mail body: asdasdasd

Example of mail that goes into Inbox folder:
Subject: Tomorrow
Mail Body: Are we having lunch tomorrow?

If I send the exact same mails from a domain that is hosted by one.com, both mails go into inbox folder.

Please tell me if I should provide you with any logs/config files.

Thanks in advance.

INFO:
Debian Lenny 32bit
ispCP 1.0.7