I received the following mail.
What should I do?
Your certificate (or certificates) for the names listed below will expire in 0 days (on 27 Sep 21 16:01 +0000). Please make sure to renew your certificate before then, or visitors to your web site will encounter errors.
We recommend renewing certificates automatically when they have a third of their total lifetime left. For Let's Encrypt's current 90-day certificates, that means renewing 30 days before expiration. See Integration Guide - Let's Encrypt for details.
For any questions or support, please visit: https://community.letsencrypt.org/ Unfortunately, we can't provide support by email.
For details about when we send these emails, please visit: Expiration Emails - Let's Encrypt In particular, note that this reminder email is still sent if you've obtained a slightly different certificate by adding or removing names. If you've replaced this certificate with a newer one that covers more or fewer names than the list above, you may be able to ignore this message.
If you are receiving this email in error, unsubscribe at:
[ r e m o v e d ]
Please note that this would also unsubscribe you from other Let's Encrypt service notices, including expiration reminders for any other certificates.
The Let's Encrypt Team