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SSL is installed but can't send encrypted emails

Discussion in 'E-mail Discussion' started by Samet Chan, Jun 7, 2018.

  1. Samet Chan

    Samet Chan Well-Known Member

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    Hi,

    It is not working for me.
    I'm on CentOS 7.5 (Core).
     
  2. cPanelMichael

    cPanelMichael Technical Support Community Manager
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    Hello @Samet Chan,

    I moved this post to it's own thread.

    The "telnet" utility isn't always installed by default. You can install it with the following command:

    Code:
    yum install telnet
    Thank you.
     
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  3. Samet Chan

    Samet Chan Well-Known Member

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    Ok, just installed telnet. They server are trying to connect after refused.
    Code:
    [root@x ~]# telnet gmail-smtp-in.l.google.com 465
    Trying 2a00:1450:400c:c09::1a...
    telnet: connect to address 2a00:1450:400c:c09::1a: Connection refused
    Trying 64.233.166.26...
    
    This IPv6 and IPv4 are from google.com, it's not my IP server.
     
  4. cPanelMichael

    cPanelMichael Technical Support Community Manager
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    Hello,

    I recommend reaching out to your data center or hosting provider to verify if there's anything filtering port 25 or port 465 traffic in their network or firewall rules. Providers will often block these ports as a SPAM prevention technique.

    Thank you.
     
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  5. Samet Chan

    Samet Chan Well-Known Member

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    I disabled CSF Firewall, but still they are trying to connect.
    Code:
    [root@x ~]# telnet gmail-smtp-in.l.google.com 25
    Trying 2a00:1450:400c:c0a::1b...
    Connected to gmail-smtp-in.l.google.com.
    Escape character is '^]'.
    220 mx.google.com ESMTP p12-v6si7373990wrd.297 - gsmtp
    
    
    [root@x ~]# telnet gmail-smtp-in.l.google.com 465
    Trying 2a00:1450:400c:c0a::1b...
    
    
    [root@x ~]# telnet gmail-smtp-in.l.google.com 587
    Trying 2a00:1450:400c:c0a::1b...
    
     
  6. cPanelMichael

    cPanelMichael Technical Support Community Manager
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    CSF firewall is a local firewall on your server. Your data center or hosting provider could filter port 465 traffic in their network or router rules outside of your individual server. Can you check with them to see if that's the case?

    Thank you.
     
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  7. Samet Chan

    Samet Chan Well-Known Member

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    Ok, I've contacted the hosting. They will reply back soon.
     
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  8. Samet Chan

    Samet Chan Well-Known Member

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    Ok, we got received an email from support hosting.
    And there,
     
  9. cPanelMichael

    cPanelMichael Technical Support Community Manager
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    Hello @Samet Chan,

    Thank you for the additional information. The telnet results over ports 465 and 587 are normal when checking Gmail, as Google blocks those connections.

    Can you let us know the specific error message you are receiving in your email client? One other item to rule out is the use of IPv6 lookups. Here are a couple of third-party URLs you may find helpful to test if this solves the problem:

    Why is my CentOS 6 system doing IPv6 lookups?
    Forcing DNS lookups to use IPv4 instead of IPv6 - CentOS

    Thank you.
     
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  10. Samet Chan

    Samet Chan Well-Known Member

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    I don't really use IPv6. I prefer to use IPv4. Gmail just keep receive of my spam folder from my site forum using 465 Port for SSL.
    And I only see in receive email for "Gray (TLS - standard encryption)", there no Green (S/MIME enhanced encryption). If I can a switch to Green (S/MIME enhanced encryption) and without check spam/junk folder?
     
  11. cPanelMichael

    cPanelMichael Technical Support Community Manager
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  12. Samet Chan

    Samet Chan Well-Known Member

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    I just read it this guide. It was not clear me to understand.
    Code:
    [root@x ~]# dig mx1.cpanel.net +short
    208.74.121.68
    [root@x ~]# dig -x 208.74.121.68 +short
    mx1.cpanel.net.
    
     
  13. cPanelMichael

    cPanelMichael Technical Support Community Manager
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    Hello @Samet Chan,

    That's the example. You should replace "mx1.cpanel.net" with your server's hostname, and then replace "208.74.121.68" with the IP address that appears when running the first command.

    Thank you.
     
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  14. Samet Chan

    Samet Chan Well-Known Member

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    Hostname was default by hosting. Do I need to contact hosting support to add this mx1.cpanel.net right?
     
  15. cPanelMichael

    cPanelMichael Technical Support Community Manager
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    No, mx1.cpanel.net is just an example. You need to use your server's actual hostname (e.g. server.yourserver.com).

    Thank you.
     
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  16. Samet Chan

    Samet Chan Well-Known Member

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    It is correct.
    Code:
    [root@x ~]# dig https://x.server.net +short
    [root@x ~]# dig -x xxx.xxx.xxx.xx +short
    x.server.net.
    
     
  17. cPanelMichael

    cPanelMichael Technical Support Community Manager
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