What I decided to do finally is the following. I removed my e-mails from OpenERP, after working some time with it I found out the e-mail client of OpenERP was seriously lacking.

1. To get my synching done with outlook I connected my google apps e-mail adresses directly to Outlook.
2. I set up my OpenERP calendars to synch with google apps. And I synched google calendar with Outlook.
3. I defined the mailto links in my browers to open up Outlook. Which means that when I go to clients in OpenERP and I press on an e-mail adress of a client an Outlook windows opens up, ready for me to send a message.

This is the best solution I found to manage your e-mails and calendar with OpenERP. The integration with OpenERP is very basic, I can't link an e-mail to an opportunity/clients but it's simple and it works, so I guess it's fine. The methodology I used can also be applied for thunderbird.