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SMTP downtime --- Important

Discussion in 'E-mail Discussions' started by linuxgirl, Sep 6, 2007.

  1. linuxgirl

    linuxgirl Active Member

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    Hello,

    Now a days we are facing some strange results about SMTP downtime.
    We manage more than 15 cpanel + exim servers but now we a days we are getting SMTP down alert for 4-5 servers at a time.And if we check the logs the service is actually stoped.One more thing i have observed that the cpanel version is 10.8 of the server which get SMTP down frequently. Is this version can cause the downtime of smtp?

    Please update me the same.

    Thank you.


    !Linuxgirl!
     
  2. nyjimbo

    nyjimbo Well-Known Member

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    Is the alert coming from chkservd, the normal monitor on the cpanel server?. Are you sure it remains down, its best to telnet to port 25 of that server to see if you get a response rather than look at the status via WHM or Cpanel as sometimes the thing needs 5 minutes to update.

    Some kind of weird new spamming technique is going around that is hanging onto smtp connections for long periods of time and filling up the max connects so SMTP stops responding with normal 220 messages and Cpanel chkservd sees it as a dead EXIM and restarts it.

    See this thread for some possible ideas or things you can check:

    http://forums.cpanel.net/showthread.php?t=70471
     
  3. cPanelNick

    cPanelNick Administrator
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    Spammer have come up with a new technique which basically amounts to a denial of service attack against your smtp server. Tonight's CURRENT build will be more aggressive at stopping it.
     
  4. cPanelDavidG

    cPanelDavidG Technical Product Specialist

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    For those following this thread, the new build of CURRENT and EDGE are now available :).
     
  5. koolcards

    koolcards Well-Known Member

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    I've seen a lot of these threads concerning mail servers mysteriously restarting or even failing several times a day. On my own servers, I've seen quite an increase in the number of dictionary email attacks daily over the recent weeks and have to guess that your server load would depend on how much work you have your machine put into each unassigned piece of mail.

    I can imagine if each has to be checked against external lists (RBL), along with other anti-spam or spam detecting techniques, that an awful lot of external connections along with their associated processes are being opened while more and more emails arrive, until system resources fail.

    I just did a search on Dictionary email attacks and saw this (from somebody familar around here) that might help some server setup's.

    http://www.configserver.com/free/eximdeny.html
     
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