The Gandi Mail product is provided as a complementary service provided with domain names registered at Gandi. It is not, and never was, intended to be a "public" email (SMTP) relay service, despite it only being accessible after authentication. Of course, we also provide bolt-on functionality, at a modest cost, for our customers who require additional features such as additional storage space, more than five mailboxes, and auto-responders, etc. Nevertheless, the Gandi Mail service is only to be used for the sending and receiving of mails for our customers' domains registered with us.
Unfortunately, over the past several months a large number of users have been using the service to send emails "from" other domains, either not registered at Gandi, or in many cases domains which are entirely bogus. The vast majority of such emails have been revealed to be spam and/or "phishing" attempts.
As a result, effective immediately, and as part of the implementation of the new Gandi Mail platform, the Gandi Mail servers will only allow sending of emails from the customer's domain registered at Gandi. If the "from" address of the email does not meet this criteria, it will be rejected.
Again, we apologize for having to take such drastic action without notice, but these measures had to be put in place to protect not only the mail infrastructure itself, but also the quality of service for you, our customers, the vast majority of whom do indeed use the mail service responsibly and in the manner in which it was intended.
As usual, should you encounter any problems with your Gandi Mail service, please do not hesitate to contact our support team who will be happy to assist.