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Outgoing smtp connections, to local Exim

Discussion in 'E-mail Discussions' started by mikelsanz, Nov 20, 2017.

  1. mikelsanz

    mikelsanz Member

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    Hello! We have some hosts with Wordpress installs, with a plugin to change mail() function, to external SMTP gateway. From last upgrade to v.68, we can't use this, and all the outgoing smtp attempts, goes to local Exim, and not outside...

    Connection: opening to ssl://externalgateway:465, timeout=300, options=array ()
    Connection: Failed to connect to server. Error number 2. "Error notice: stream_socket_client(): Peer certificate CN=s3.localnameserver.xxx' did not match expected CN=mail.externalgateway.xxx'
    Connection: Failed to connect to server. Error number 2. "Error notice: stream_socket_client(): Failed to enable crypto
    Connection: Failed to connect to server. Error number 2. "Error notice: stream_socket_client(): unable to connect to ssl://externalgateway.xxx:465 (Unknown error)
    SMTP ERROR: Failed to connect to server: (0)

    -----------------------------

    smtp:none:plain://mail.externalgateway.xxx':587 <--- Calling to external gateway

    220-s3.example.com ESMTP Exim 4.89 #1 Mon, 20 Nov 2017 13:00:52 +0100
    220-We do not authorize the use of this system to transport unsolicited,
    220 and/or bulk e-mail.
    EHLO 185.162.171.12
    250-s3.localnameserver.xxx Hello XYZ.XYZ.XYZ.XYZ [XYZ.XYZ.XYZ.XYZ] <--- But connected to local Exim...
    250-SIZE 52428800
    250-8BITMIME
    250-PIPELINING
    250-AUTH PLAIN LOGIN
    250-STARTTLS
    250 HELP
    AUTH PLAIN
    334
    AHdlYnNAZW52aW9zLjIwY29tdW5pY2FjaW9uLm5ldABzbXRwMjAxNCs=
    535 Incorrect authentication data
     
    #1 mikelsanz, Nov 20, 2017
  2. cPanelMichael

    cPanelMichael Forums Analyst
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    Hello,

    Can you verify if the "WHM Home » Security Center » SMTP Restrictions" feature is enabled on this system? If so, does disabling it solve the issue?

    Thank you.
     
    #2 cPanelMichael, Nov 20, 2017
  3. Anas Ashfaq

    Anas Ashfaq Registered

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    Hello,

    Disabling the restrictions solves the issue but is that a recommended solution?

    Is there a way to enable the smtp restrictions and add an exception to the trust mail sending providers e.g. mailgun

    Thank you
     
    #3 Anas Ashfaq, Jan 15, 2018
  4. cPWilliamL

    cPWilliamL cP Technical Analyst II
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    We don't provide a method at this time to make this option specific to users or outbound hosts; however, this is simply implemented through iptables UID/GID matches:
    Code:
    # iptables -nL|grep match
ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0            multiport dports 25,465,587 owner GID match 992
ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0            multiport dports 25,465,587 owner GID match 12
ACCEPT     tcp  --  0.0.0.0/0            127.0.0.1            multiport dports 25,465,587 owner UID match 202
ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0            multiport dports 25,465,587 owner UID match 0
    It shouldn't be difficult to apply manually, but this would also make a good feature request. I also believe CSF(ConfigServer Security and Firewall) provides this functionality.
     
    #4 cPWilliamL, Jan 16, 2018
    kawasakai likes this.
  5. kawasakai

    kawasakai Active Member

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    Hello,

    My current rule to allow reaching external SMTP servers for a certain user looks like:
    Code:
    iptables -t nat -I OUTPUT 5 -d 1.2.3.4 -p tcp -m multiport --dports 25,465,587 -m owner --uid-owner 1036 -j RETURN
    Now I need some advice how to to apply this rule permanent, in in a way which doesn't disturb cPanels own ruleset.
     
    #5 kawasakai, Apr 10, 2018
    Last edited: Apr 10, 2018
  6. cPanelMichael

    cPanelMichael Forums Analyst
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    Have you considered using CSF to manage the firewall rules? CSF offers options that allow you to restrict SMTP similar to the SMTP Restrictions option in WHM, but with more control over specific users:

    ConfigServer Security & Firewall (csf)

    Or, you could simply use CSF to manage your own custom firewall rules to ensure they are preserved through restarts.

    Thank you.
     
    #6 cPanelMichael, Apr 10, 2018
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