Steps to take to keep exiting mails from ending in destination junk box

[Rick]

I've got a fresh install debian wheezy x64 with Kolab 3.3 , I'm testing this system and sending emails to my own addresses in gmail and microsoft.
They all end up in the junk mail folders.
What steps need to be taken to make sure emails being sent from a Kolab instance do not get flagged by these systems.

Thanks
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