Mailstore - validation of challenge failed

Hello, I’m trying to install mailstore ( using a Let’s Encrypt certificate is pointing to my public IP and port 80 is forwarded to the server, but I get the error detailed below. Can anyone point me in the right direction?

Thanks in advance

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My domain is:

I ran this command: Mailstore server installer (as administrator)

It produced this output:

Starting certificate enrollment for ‘’…
To verify your configuration a certificate is requested from the Let’s Encrypt Staging environment.
Signing in to Let’s Encrypt Staging environment…
Initializing certificate enrollment for
Initializing validation challenges…
Starting HTTP validation server on port 80…
Initiating validation…
Waiting for validation process to finish…
Validation of challenge has failed.
Error Code: BadRequest
Error Type: urn:ietf:params:acme:error:connection
Error Detail: Fetching Timeout during connect (likely firewall problem)

My web server is (include version): N/A

The operating system my web server runs on is (include version): Windows Server 2019 Standard

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): N/A

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

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

Hi @PieCaptain

your output (Timeout) says: Your configuration doesn’t work.

Runs your server? Is there a http webserver? Works that server internal?

It seems perhaps the ports are forwarded, but they are being blocked by the host.

80/tcp   filtered http
135/tcp  filtered msrpc
139/tcp  filtered netbios-ssn
443/tcp  filtered https
445/tcp  filtered microsoft-ds
8081/tcp filtered blackice-icecap
8082/tcp filtered blackice-alerts

Maybe Windows Firewall or something like that?

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