Croissant does not offer mailing addresses. Some of the spaces in the Croissant network may offer a mailing address but it would be completely separate from your Croissant membership. You can inquire with the community manager directly about pricing and availability for your virtual mailbox.
You may not send mail to any coworking space in the Croissant network without first setting up a virtual mailbox.
Alternatively, many members have had success using these services:
New York: NY Mail