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