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clients IP keep getting black list - please help

Posted by triple, 06-17-2009, 02:04 AM
Hello every one, I have 20 clients who are on different networks and countries but all of the sudden their IP's are keep getting black list in spamhause, CBL, dsbl etc and they can not send email i am so very tired of this, please please help me!!!!!!!!!!!!!!!! where is the real problem? how can i solve it? Waiting for your reply. Thanks.
Posted by InstaCarma_Support, 06-17-2009, 03:48 AM
Are you sure that it is your clients' IP that are being blocked and not your mail server's IP itself?
Posted by triple, 06-17-2009, 04:04 AM
I am 100% sure my mail server is all clean i check it but when i checked their network IP's it was black listed? I have just 20 customers and all are complaining how do those big companies like hostgator and howay handling this issue? I had to take off all of the CBL,SPAMHAUSE etc DNS from my mail server so they can still send email till i find solution. Please help me.
Posted by RandomThoughts, 06-17-2009, 04:27 AM
I find it hard to believe that 20 clients, each on different networks, would all have their IP's blocked at the same time. I'm assuming they use your mail server for sending email, are you sure it's not your mail server's IP that's blocked, what checks have you made?
Posted by mugo, 06-17-2009, 04:54 AM
Spam isn't the only thing that can get you blacklisted. No reverse dns, or mismatched, or a bad HELO domain used by your SMTP server (if you machine is Linux, is the host name set correctly?), and different technical reasons can land you on block lists also. You mentioned CBL, and they list just for these reasons, especially the bad HELO domain. Can you list some of the evidence the sites should have listed against you? Most do.
Posted by jNive, 06-17-2009, 05:13 AM
indeed - if they are using your systems for that mail - sounds like it is your IPs being blacklisted. if sending mail via your systems, only your outgoing/internet facing IP will end up being checked by the target systems generaly. Might be worth letting us know the mailserver IP (in private if you prefer naturally) so people can do a quick check. It highly improbable that your client's IP blocks would actually get listed in spamhaus repeatedly Last edited by jNive; 06-17-2009 at 05:17 AM.
Posted by mwatkins, 06-17-2009, 12:34 PM
Folks: Unless I am mistaken this person's server isn't blacklisted; his server is blocking retail ISP clients from sending SMTP mail via his server. A common configuration I might add. Lets take a step back here. It sounds like these are their ISP's IP's you are talking about, not yours. Correct? (Emphasis mine) It appears as if you are permitting them to send mail *through* your server via SMTP. Not a problem, but if you are subscribing to particular RBL's you are bound to have at least one in there which checks the sender's IP against known retail ISP dynamic IP blocks. Since a ton of spam originates from compromised machines sitting on ISP networks, it makes sense to block mail from a dialup or cable / dsl retail ISP block. That is what appears to be your issue - clients around the world are trying to send SMTP mail to you directly from their desktops rather than via their ISP's mail server. Have one of them change their email client software to route their mail via their ISP to confirm. If indeed you have clients that need or must for some vanity reason send mail through your server directly, then you'll have to set up SMTP authentication (either pop/imap before SMTP or proper SMTP auth) which allows your clients to bypass the RBL check, and/or simply whitelist the IPs. The latter is not such a good idea because a) dynamic IPs change and b) spoofing an IP remains a possibility for spammers to get through your server's defences. B is probably less of an issue in reality but A is definitely an ongoing management headache. Last edited by mwatkins; 06-17-2009 at 12:38 PM.
Posted by mugo, 06-17-2009, 07:06 PM
He has been listed on CBL, and this is an "smtp misconfiguration" list. I don' think it's spam related, I think his issue is CON-figuration of his smtp server, and possibly his IP-based stuff...rDNS, etc. CBL most commonly lists for invalid "HELO" domains (ie - they have left their Linux mail server running sendmail's hostnmae as "localhost"). Probably other issues, but it you are truley listed on CBL, this IS and issue. Period.

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