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 pop3.moonpoint.com:995 (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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