Let's Encryipt enabled but I get error message on Outlook

Discussion in 'General' started by deividmen, Dec 11, 2019.

  1. deividmen

    deividmen New Member


    I have an Ubuntu 16.04 server with ISPConfig 3.1 and many websites installed. I also set up Postfix with an SMTP relay service for reliable email delivery (TurboSMTP).

    I have enabled SSL with Lets Encrypt using built-in ISPConfig 3.1 ability by following this tutorial:


    It works with https websites hosted, but the email clients do not work, and I keep getting this error message on Outlook:

    The Server you are Connected to is Using a Security Certificate that Cannot be Verified

    Any ideas?
    Last edited: Jan 15, 2020
  2. fluidmindorg

    fluidmindorg New Member

    The first thing to check is what certificate Outlook is actually getting. When it tries to connect and gives you that error, does it give you the option to view the certificate that it's having a problem with? If so, copy the details of that cert and post them here so we can see what it's getting. (It sounds like it's not getting the correct cert.)
  3. Jesse Norell

    Jesse Norell ISPConfig Developer Staff Member ISPConfig Developer

    Additionally, if you list your actual domain and server names here, others could do a quick check to see what is presented.

    Another possibility is that you need to configure your server to include the certificate chain files.
  4. Steini86

    Steini86 Active Member

    Have you restarted the (mail) server?
    Check certificate with:
    openssl s_client -showcerts -connect mail.example.com:993
    fluidmindorg likes this.

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