intermittent connectivity to mail host

Posted on 2012-09-18
Last Modified: 2012-10-01

i have a newly loaded server standard 2008 r2 setup and running like a charm, apart from one problem, at random times we stop recieving mail and then i see when i ping this mail host it doe snot respond from any client pc in the network, however this mail does respond when i ping it from the domain controller running server 2008 standard and dc, dns.

why would my users stop having access to this mail host at random times ? the mail is down for about 5 -15 minutes at a time, and comes back online by itself , i have confirmed that the ISP where the mail server is hosted, has put me on all the whitelists, on their side, as well as phoned my ISP to see if my link is not maxing out or flapping - and they say no, the link is running at less than half its capacity most of the time.

so now i dont understand why ? i have 2 layer 2 3com switches which has nog special configs on them,

i have a feeling it might be a trust issue between this mail host that runs exim smtp and my newly created domain controller but i am not sure, can anyone point me in the right direction of why i would be able to ping this mail host perfectly from the server but it times out randomly for periods of up to 15 minutes at a time from any client pc of the network ?

Question by:safsystech
    LVL 35

    Expert Comment

    by:Cris Hanna
    Is the mail server in your lan or external 3rd party?

    Author Comment

    the mail server is external to our lan, based at the company that hosts the website as well.
    when the mail then drops from inside the office, only the users seem to be affected, but i still can ping that mail server perfectly from the domain controller (server standard 2008 R2 46bit) my dc also runs dns, dhcp.
    LVL 35

    Expert Comment

    by:Cris Hanna
    Have you considered adding an entry for the mail server in you're own DNS?  Additionally are using Root Hints for external resolution or DNS forwarders?

    Author Comment


    1. added the mail server as an A record,
    2. root hints are selected if it does not find forwarders
    3. forwarders are the ISP's external DNS

    but when this happens, the users can ping any website but not the mail host. this is what is so odd to me.
    LVL 42

    Accepted Solution

    Get a copy of Pingplotter (the free version is at the bottom)
    It is a visual traceroute program.  Run it and trace the path to the mail server on a workstation.  The second column is Packet Loss (PL%) and it regularly find either failing or overwhelmed machines in the path.  After that, it can be a royal PITA to get TW/Comcast/whomever to fix it; but, at least you'll know where the problem is.

    Author Closing Comment

    Thank you very much !

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