mail.client1.com mail.client2.com mail.client3.com SSL certificated

Sorry I can't explain myself well, I hope someone can understand.

When you try to set a valid certificate to mail.yourserver.com to manage emails, follow the page
https://www.howtoforge.com/securing...server-with-a-valid-lets-encrypt-certificate/
it works correctly for the first one.
My question is the following:
In a VM with ispconfig, I'm managing 10 domains.
I want to set each IMAP and SMTP server as mail.client.es.

What should I do to have a mail.client for each client?

 

Hi
I've done that... but when I set up email on my phone, I get a certificate error.
You guys explained how to do it on the page I mentioned in the previous post, but of course, for a single domain.
Using AI, it suggests:
and I was wondering if it is like that... should I do it like this?

Generate SSL Certificates for Multiple Mail Domains (acme.sh + Manual DNS-01 Challenge)
1️⃣ Install acme.sh (if not installed yet)
Run this on your server:
curl https://get.acme.sh | sh
After that, restart your shell or reload the profile:
source ~/.bashrc
2️⃣ Issue the certificate using manual DNS validation
Run the following command (replace the domains with your actual mail domains):
acme.sh --issue --dns --yes-I-know-dns-manual-mode -d mail.client1.com -d mail.client2.com -d mail.client3.com
This tells acme.sh to use the manual DNS challenge for multiple domains.

️ 3️⃣ acme.sh will prompt you to create DNS TXT records
For each domain, it will give you something like this:

Please add the following TXT record:
Domain: _acme-challenge.mail.client1.com
TXT Value: xxxxxxxxxxxxxxxxxxxxxxx

Domain: _acme-challenge.mail.client2.com
TXT Value: yyyyyyyyyyyyyyyyyyyyyyy

Domain: _acme-challenge.mail.client3.com
TXT Value: zzzzzzzzzzzzzzzzzzzzzzz

️ 4️⃣ Go to your DNS provider (Unelink in your case)
For each domain, create a new TXT record:

Record Name Record Type Value
_acme-challenge.mail.client1.com TXT xxxxxxxxxxxxxxxxxxxxxxx
_acme-challenge.mail.client2.com TXT yyyyyyyyyyyyyyyyyyyyyyy
_acme-challenge.mail.client3.com TXT zzzzzzzzzzzzzzzzzzzzzzz
⏳ 5️⃣ Wait for DNS propagation
This can take a few minutes (or up to an hour, depending on your DNS provider).
You can check the propagation using:
dig TXT _acme-challenge.mail.client1.com +short
Repeat for each domain.
Once you see the correct TXT values, proceed.

6️⃣ Finalize the certificate generation
Return to your terminal (do not close it!) and press Enter in the acme.sh prompt to continue.

acme.sh will then validate the DNS records and issue the certificates.

7️⃣ The certificates will be saved in ~/.acme.sh/
You’ll find the certificate files here:
~/.acme.sh/mail.client1.com/
├── fullchain.cer
├── mail.client1.com.key
These are the files you will use in your Postfix and Dovecot configuration.

8️⃣ Renewal (in the future)
Every 90 days, you will need to repeat this process:
make a script that does it for you

• Run the same acme.sh --issue command.
• Create new TXT records with updated values.
• Wait for propagation.
• Finalize the validation.
  

 

Then
the section

cd /etc/postfix/
mv smtpd.cert smtpd.cert-$(date +"%y%m%d%H%M%S").bak
mv smtpd.key smtpd.key-$(date +"%y%m%d%H%M%S").bak
ln -s /root/.acme.sh/mail.example.com/fullchain.cer smtpd.cert
ln -s /root/.acme.sh/mail.example.com/mail.example.com.key smtpd.key
systemctl restart postfix
systemctl restart dovecot​

Shouldn't this be done?

I create the site mail.mydomain.es and check the certificates.
When I create the new account and in the IMAP and SMTP servers, can I enter mail.mydomain and it will correctly pick up the certificates and I won't get the message that the connection may not be secure?

Well, on the first client, I was getting a certificate error until I followed the instructions at https://www.howtoforge.com/securing...server-with-a-valid-lets-encrypt-certificate/
On the next one, those instructions stopped working, and I started having problems with the Dovecot and Postfix servers.

 

I have 50 clients on a single cPanel.
The idea is to separate it into three servers plus two large clients that will be on their own server. I manage everything, including DNS. The clients don't do anything, at most, migrating to another server.

cPanel manages certificates well. It creates a certificate for each client subdomain, and I don't have to do anything. Everything works.
But of course, it's very expensive. I really like ISPconfig. The only thing missing is precisely that and a file manager.

Between mobile devices, Outlook, and other applications, I have over 700 applications that I should move from mail.yourdomain to myserver.
Which is too much work for the migration, so I'm trying to make the server mail.yourdomain so everything is transparent for my clients.
I only have 50 clients, and they're separated into three ISPconfig servers. I think the limit was 100?

I swear I followed everything, but I'll check again.
Thanks.