How do I export my contacts from an email client to a csv file?

From Outlook Express:
1. From the “File” menu, select “Export".
2. Select "Address Book".
3. “Address Book Export Tool” window will open up.
4.  Select “Text File (Comma Separated Values)”.
5.  Click “Export”.
6.  Type a file name in the "Save exported file as" input box. For example, type "mycontacts.csv" and browse to C:\  drive.
7.  Click "Next" and check only “Name” and “E-mail address”.
8.  Click "Finish" once the exporting is completed.
9.  Click the “Close” button for “Address Book Export Tool” window.

You're now ready to import the newly exported Outlook Express address book (eg: C:\mycontacts.csv).

From Microsoft Outlook:
1. From the “File” menu select “Import & Export".
2. Select “Export to a file” and click on “Next”.
3. Select “Comma Separated Values (Windows)” and click on “Next”.
4. Select “Contacts” and click on “Next”.
5. Type a file name in the "Save exported file as" input box. For example, type "mycontacts.csv" and browse to your C:\ drive.
6. Click “Next”.
7. Click “Finish”.

You're now ready to import the newly exported Microsoft Outlook address book (eg: C:\mycontacts.csv).