Fixing Gmail issue: TLS Negotiation failed, the certificate doesn't match the host

Discussion in 'ISPConfig 3 Priority Support' started by miguelpinheiro, Apr 14, 2020.

  1. Hi! I came across an issue sending email through Gmail using my ISPConfig Server. It seems Gmail recently checks the certificate that matches the mail server. You can check more details is the following image:


    Also I'm following the issue in this Google Community forum. As some people points out in the thread, it seems things get fixed adding a Letsencrypt certificate to SMTP servers. I have 2 mail servers in my server, each pointing to their own IPv4 address: => address 1 => address 2

    Although I have in my server several domains using LetsEncrypt (i.e. and I can't figure out, how can I add a LetsEncrypt certificate to or and if this is achievable using ISPConfig3.

    I appreciate any help on this. Best regards.

  2. till

    till Super Moderator Staff Member ISPConfig Developer

  3. Taleman

    Taleman Well-Known Member HowtoForge Supporter

  4. Thank you @till
    After running the script I got:
    ./ line 28: certbot: command not found
    It seems I do not have certboot installed in my Debian Jessie. I tried to install using:
    apt-get install certbot
    But I have some unmet dependencies.:(

    Reading package lists... Done
    Building dependency tree
    Reading state information... Done
    Some packages could not be installed. This may mean that you have
    requested an impossible situation or if you are using the unstable
    distribution that some required packages have not yet been created
    or been moved out of Incoming.
    The following information may help to resolve the situation:
    The following packages have unmet dependencies:
     certbot : Depends: python3-certbot (= 0.28.0-1~bpo9+1) but it is not going to be installed
    E: Unable to correct problems, you have held broken packages.
    This is a prod server. I'm not confident enough to fix this. Can I have hire paid support?
  5. till

    till Super Moderator Staff Member ISPConfig Developer

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