issue is now fully resolved by mailersend, and we got a valid certificate so we can activate our domain links.container-registry.com again.

We disabled the custom domain links.container-registry.com and are now using the default domain of the mail provider mailersend.

One of the email delivery services we are using to send confirmation and welcome emails is affected by the recent lets encrypt revocation of 2 million certificates.

Affected are users who signed up to exo.container-registry.com and want to confirt their account activation.

• https://community.letsencrypt.org/t/2022-01-25-issue-with-tls-alpn-01-validation-method/170450
• https://www.theregister.com/2022/01/26/lets_encrypt_certificates/

Our domain links.container-registry.com is on the list of the affected domains.

curl -X POST -d "fqdn=links.container-registry.com" https://tls-alpn-check.letsencrypt.org/checkhost"

[links.container-registry.com]: The certificate retrieved from your web server has serial 04b605b34a2d1e25fc4cc3218cac6fea4fa7 and was found in our affected data set. Please renew your certificate as soon as possible. Help is available at https://community.letsencrypt.org/t/questions-about-renewing-before-tls-alpn-01-revocations/170449