Update: As of now, the staging environment has TLS-SNI fully disabled. We’ve also disabled the “reuse valid authorizations” feature in staging for the next 30 days. This will ensure that each staging dry run issuance does a fresh validation, so you can be confident that if validation in the staging environment succeeds, your client is working correctly.
Also, we’re changing the final end-of-life date for TLS-SNI in production to March 13, 2019. This will give more people time to update. We’re going to use the original February 13 date as the beginning of a brownout period: We will disable TLS-SNI validation in production on February 13, then re-enable it a week later. We may choose additional brownout periods before the final deprecation.
The goal of the brownout periods is to catch the attention of people who may have missed the notification emails. Not every certificate will necessarily renew during that window, but hopefully enough it will increase the number of people who notice and can update ahead of the deadline.
We’re planning to send out a second round of notification emails with the updated information tomorrow.