The French ISP Orange is shutting down email service on the domain voila.fr. Service is expected to end on January 15, 2016. At some point after this date, expect any email to voila.fr addresses to be rejected.
The online shutdown FAQ explains (in French) that users have another email address already, and it tells them how to lookup that username and password. It also makes it clear that users will not be able to access their voila.fr mailbox or any previously received messages after the service is shutdown.
Senders might want to take advantage of the window before the service is fully retired to email those users and request that they provide you with an updated subscriber email address.
Update: An anonymous friend offers the following clarification:
The FAQ states that a redirect (forward) can be set up to another address (and provides details on how to do that) and that the forwarding will be active for the next 6 month after the service shutdown (around June 15th 2016).
Of course, a majority of users won't bother to enable forwarding, but I would still advise against blocking mail to voila.fr altogether immediately from January 15th onward. There will still be active users due to this forwarding functionality, and actually I think that those who bother to do it are the most likely to be engaged or using a voila.fr address as as a primary address (or an important one at least).
Just make sure to process bounces efficiently, and if a voila.fr address doesn't bounce after the shutdown date, you know that the user is active on this channel and interested in keeping in contact, and you have 6 months to ask him to opt in with his/her new address.
Thanks, anonymous friend!