1. Open Outlook 2010 and click File > Options.
2. When the Outlook Options window opens, click Advanced. In the right pane, click the Export button.
3. In the Import and Export Wizard window, select the Export to a file option, then click Next.
4. Under Create a file of type:, select the Comma Separated Values (Windows) option to create a CSV file.
5. Under Select folder to export from:, select the Contacts folder you would like to export, then click Next to continue.
6. Under Save exported file as, click Browse to select a destination folder.
7. In the File name: box, type a descriptive name for your contacts file, then click OK.
8. Click Next.
9. Complete the process by clicking Finish.

You have now exported your contacts to a file that will allow you to migrate your address book into another email client.