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From: Wietse Venema (wietse_at_porcupine.org)
Date: Mon Feb 03 2003 - 14:34:33 CST

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    Greg Hackney:
    >
    > Postfix here is having occasional DNS timeout problems.
    >
    > It's caching DNS forwards through a couple of private
    > chained DNS servers before hitting the public's DNS servers.
    >
    > Some of the public's DNS servers are occasionally a bit slow to respond,
    > and some of those use short expiry intervals, so the MX and A data isn't
    > always cached locally.
    >
    > Am I correct in that Postfix itself has no configurable DNS timeout
    > parameters?

    Correct. Postfix invokes the client routines in resolver(3) which
    hide all the gory details of querying a server.

    > Also, am I correct that Postfix invokes res_query(), which uses
    > BIND's resolver library, which uses RES_TIMEOUT, which is defined in
    > /usr/include/resolv.a (5 seconds). And therefore statically linked
    > Postfix binaries would need to be relinked with a new libresolv.a
    > library whose RES_TIMEOUT has been increased?

    Neither FreeBSD 4.7 nor 7.3 document RES_TIMEOUT.

            Wietse