If you want to export the contacts for a particular mailing list, you can do this by selecting the downward pointing arrow as highlighted in the following image next to the mailing list and then select the export option from the list :
If you'd like to export all contacts from a user account, can do this as follows:
1. Go to the Measure area and then select the 'Export' option from the list to the left.
2. Select the Contacts option as highlighted in the following image:
3. You can export contacts either by mailing list or all at once. Please note: If you're looking to export a very high volume of contacts (1000+) and are encountering issues, please contact email@example.com.