I just got this email. However, I host many wabsites (not all of them on the same server). I guess that one of the server is using an old version on the certbot client, but I'm not sure which. I however have a list of all the domains I host. Is there a command available to know which of them is using the old validation method ?

For reference, here is the email I got from Let's Encrypt on my contact email:


Action is required to prevent your Let's Encrypt certificate renewals from breaking.

Your Let’s Encrypt client used ACME TLS-SNI-01 domain validation to issue a certificate in the past 60 days.

TLS-SNI-01 validation is reaching end-of-life and will stop working on February 13th, 2019.

You need to update your ACME client to use an alternative validation method (HTTP-01, DNS-01 or TLS-ALPN-01) before this date or your certificate renewals will break and existing certificates will start to expire.

If you need help updating your ACME client, please open a new topic in the Help category of the Let's Encrypt community forum:


Please answer all of the questions in the topic template so we can help you.

For more information about the TLS-SNI-01 end-of-life please see our API announcement:


Thank you, Let's Encrypt Staff

  • 1
    maybe the package ssl-cert-check (debian, ubuntu) could help – Max Jan 18 at 8:57
  • 1
    Just update certbot on all your servers. That should take about a minute. – Michael Hampton Jan 18 at 16:44

I received the same email. After reviewing the information in a post titled, "How to stop using TLS-SNI-01 with Certbot" in the help link, they provided this command to determine if you need to:

grep '^pref_challs.*tls-sni-01' /etc/letsencrypt/renewal/*

They also suggested you update Certbot before running the command.


I tested my domain name on this site: https://letsdebug.net/ (mentioned on the let's encrypt forum : https://community.letsencrypt.org/t/third-party-tools-to-check-your-configuration/76272). I tested these alternative methods of validation (HTTP-01, DNS-01 or TLS-ALPN-01) and all my domains are OK. You can already do this manipulation. Best regard.

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