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Reverse DNS does not match SMTP Banner

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24 comments

  • cPRex Jurassic Moderator
    Hey there! I'm sorry to hear about the issues with the reverse DNS configuration. The reverse DNS should point to the hostname of the server. However, there isn't a way to fix it on the server itself - you *have* to contact your hosting provider or datacenter to have them set that up. Once they do that, it should start working immediately for you.
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  • oomaro
    I can receive Emails. I can't send emails. and after I tried all the methods here I got only this " Reverse DNS does not match SMTP Banner " you know I rebuilt the VPS. the problem still exists. I contacted the DC provider he said contact cpanel admin.
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  • quietFinn
    Your DC provider is an idiot o_O
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  • cPRex Jurassic Moderator
    @oomaro - you would first want to confirm the reverse DNS is in place. You can do that with the "dig -x" command, or with an online tool like Reverse IP Lookup - MxToolbox. If that works properly, can you check and see if there are any customizations to the /etc/mailhelo file on the system? By default, this file should contain one line, that looks similar to the following: *: host.domain.com
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  • oomaro
    whatever you think I tried it. but the problem still I can receive emails. I can't Send. it hung in queue mail.
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  • oomaro
    @oomaro - you would first want to confirm the reverse DNS is in place. You can do that with the "dig -x" command, or with an online tool like
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  • cPRex Jurassic Moderator
    These specific errors aren't related to the reverse DNS. Have you worked through all the options listed here?
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  • oomaro
    I did it but that /scripts/mailperm $user given me nothing.
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  • cPRex Jurassic Moderator
    That's normal - there may not be output from that command. For the mails that are sitting in the queue, what does the Exim log show? The full mail transaction would be in /var/log/exim_mainlog.
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  • cPRex Jurassic Moderator
    I removed that last post because it was just too much information. We just need to see one specific failed email transaction in the log showing what is currently happening on the system.
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  • quietFinn
    You can do: exigrep "Message ID" /var/log/exim_mainlog Message ID you can see in Mail Queue Manager.
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  • oomaro
    I removed that last post because it was just too much information. We just need to see one specific failed email transaction in the log showing what is currently happening on the system.

    how can I attach it here text not allowed
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  • oomaro
    I also open ticket with cPanel. they said open port 25 does not open I don't have external firewall. cPanel said check with you DC VPS provider. DC VPS admin said Problem with cPanel and EXIM. specially happened. If I have domains. but if I have only one domain it will work fine. I hate to be like a Pingping ball.
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  • cPRex Jurassic Moderator
    Can you please let me know the ticket number you have opened with us?
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  • oomaro
    95126929
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  • cPRex Jurassic Moderator
    Thanks for that. That confirms that outbound connections over port 25 are being blocked by your hosting provider. This is very common, and we have details on this here:
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  • oomaro
    the port is up !!
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  • cPRex Jurassic Moderator
    That test makes an inbound connection. Can you run this command from your server? telnet gmail-smtp-in.l.google.com 25
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  • quietFinn
    Usually telnet is not installed by default, in that case you can install it: yum -y install telnet
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  • oomaro
    Usually telnet is not installed by default, in that case you can install it: yum -y install telnet

    it is ok I am an expert in Linux.
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  • oomaro
    also I got this now
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  • mtindor
    If your server IP address is the 135.181.xxx.yyy address, it reverse resolves to static.yyy.xxx.181.135.clients.your-server.de Is the hostname of your server (as configured in WHM) really static.yyy.xxx.181.135.clients.your-server.de ? I can't tell because when I try to connect to the mailserver on 135.181.xxx.yyy it is refusing mail from my country lol. Nice one. Anyway, if your hostname as configured in WHM is something other than static.yyy.xxx.181.135.clients.your-server.de, then your reverse DNS is not set up properly.
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  • ITHKBO
    Isn't this message a well known false positive with mxtoolbox due to the way EXIM SMTP transaction delay works?
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  • cPRex Jurassic Moderator
    Yes, part of this issue is due to the SMTP delay.
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