Can I make a certificate for a CNAME'd subdomain?

My domain is:

I ran this command: certbot certonly --standalone -d,

It produced this output:

You have an existing certificate that contains a portion of the domains you
requested (ref: /etc/letsencrypt/renewal/

It contains these names:

You requested these names for the new certificate:,

Do you want to expand and replace this existing certificate with the new

(E)xpand/©ancel: E
Renewing an existing certificate
Performing the following challenges:
http-01 challenge for
Cleaning up challenges
Problem binding to port 80: Could not bind to IPv4 or IPv6.

My web server is (include version): Apache2 2.4

The operating system my web server runs on is (include version): Debian Buster

My hosting provider, if applicable, is: N/A

I can login to a root shell on my machine (yes or no, or I don’t know): Yes

I’m using a control panel to manage my site (no, or provide the name and version of the control panel): No

The version of my client is (e.g. output of certbot --version or certbot-auto --version if you’re using Certbot): 0.31.0

As you can see in the output creating the certificate for this new subdomain (webmail) doesn’t work.
The subdomain is a CNAME that points to the first one, that already has a cert (see output, again).

Re-trying to issue the cert for the first sub-domain alone (deb-mail) works, but not with the CNAME’d entry.

They are supposed to point exactly to the same place… (and they do, if I make a security exception on Firefox, does connect me to
I’d just like to not show this exception, thus, to create a certificate that covers both these domain.

Any idea why it doesn’t work in my case ?

Hi @oukourj


is already a running webserver. So you can't use --standalone, that's simple.

Use webroot or the same authenticator you have use with your other domain name.

It's not a problem of CNAME.


It works in webroot, without using --standalone, thanks.

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