unfortunately, apple’s addressbook only includes the following two formats for export of your contacts: vcard (.vcf) or archive (.abbu).
both formats serve their purpose well, however they do not allow for export into a plain text file or .csv for easy import into a list editor of your choice, google mail or mailchimp.
fortunately, antonio lorè has created a little utility called ‘addressbook2csv exporter‘ and makes it available for free. ‘addressbook2csv exporter’ let’s you choose which fields to export and then creates a csv file which can be easily processed in a list editor for further import.