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Tue, Apr 05, 2022 6:05 pm

Let's Encrypt Problem binding to port 80: Could not bind to IPv4 or IPv6

A couple of users notified me that they were receiving warning messages regarding the security certificate on their email server when they were checking email with Microsoft Outlook. I checked the expiration date on the security certificate for the email server with the OpenSSL command openssl s_client -connect (the system is using Dovecot, which is an open-source IMAP/POP3 software program providing users with the ability to download their email). Dovecot listens on TCP port 995 for POP3S secure email connections for downloading email. I could see the certificae was expired and I issued the quit command when I saw the "OK Dovecot ready" prompt. The email security certificate on the system is provided by Let's Encrypt, so I then tried renewing the certificate from the root account with the letsencrypt renew command, but was unsuccessful. I found the solution was to stop the Apache web server software running on the system, thanks to a post by JuergenAuer at Renewing certificate getting error: Problem binding to port 80: Could not bind to IPv4 or IPv6. After I stopped the web server software, I was able to reissue the letsencrypt command to renew the certificate without the "Problem binding to port 80" error message. I then restarted the Apache web server software and Dovecot.

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