FastMail makes importing or exporting contacts simple. You can upload existing address books from vCard, CSV or LDIF files, and download your current address book in any of the same formats.
Note that importing and exporting is a one-time operation. If you're looking to keep your address book constantly up to date, you are probably after synchronising via CardDAV.
To import contacts into your FastMail address book:
vCardfile you want to import and click the Select button.
FastMail will import your contacts and add them to your address book. In most cases, we are unable to identify duplicates: we create a new entry for each imported contact to ensure none of your data is lost.
Unfortunately, FastMail does not support importing or exporting information about contact group membership due to limitations with external contact formats.
To export your FastMail address book:
vCard 3.0, as this is the most widely supported standard.
The address book will begin downloading. Depending on your browser settings, you may be prompted for where you wish to save it on your computer, or it may be automatically downloaded to your Downloads folder.