This incident has been resolved.

Your account is now back, of course we are still monitoring to be sure everything is now stable.
If you have any question, please open a ticket to our support team via https://www.mailjet.com/support/ticket/open

You may face some issues when accessing your account, our technical team is currently investigating, your transactional emails are properly handle.
If you have any question, please contact our support team by creating a ticket on https://www.mailjet.com/support/ticket/open