Update July 6, 2018: legacy webmail is now offline; the instructions below are defunct. If you didn't get a chance to import your old address book, please contact us and we might be able to retrieve it from backups.
We have released a new version of webmail, and are decommissioning the old application on June 18. If you would like to copy your contacts from the old to the new webmail, follow these instructions. If you do not follow these steps, you will no longer have anybody in your webmail address book.
1. Login to legacy webmail. Legacy webmail is no longer available.
2. Navigate to Options → Address Book in the sidebar, then click on the Import/Export tab, select vCard as the export format and click Export (see screenshot below).
3. Login to the new webmail.
4. Navigate to Address book, then click Import, and select the .vcard file you downloaded in step 2 (see screenshot below).