gamiddle@watmath.waterloo.edu (Guy Middleton) (06/19/91)
[Using 5.65+IDA+DECWRL sendmail] If the nameserver is temporarily out-to-lunch (usually because our link to the rest of the net is down), maphostname() (in daemon.c) will fail. This may not be the right thing to do, since the resolver sets a TRY_AGAIN status; but there is no way to let the rest of the program know that the error is a soft one. If we're calling $[...$] from the config file to look up a name, it thinks that there is no such host. We have been using the IDA extension to $[...$] (which sets a default if the host is not found) to return a "no such host" error message, but it now seems unreliable. Has anybody else encountered this problem? -Guy Middleton, Math Faculty Postmaster, University of Waterloo gamiddleton@watmath.waterloo.edu or gamiddleton@watmath.uwaterloo.ca
rickert@mp.cs.niu.edu (Neil Rickert) (06/19/91)
In article <1991Jun18.200709.18664@watmath.waterloo.edu> gamiddle@watmath.waterloo.edu (Guy Middleton) writes: >[Using 5.65+IDA+DECWRL sendmail] > >If the nameserver is temporarily out-to-lunch (usually because our link to the >rest of the net is down), maphostname() (in daemon.c) will fail. This may > >If we're calling $[...$] from the config file to look up a name, it thinks >that there is no such host. We have been using the IDA extension to $[...$] This is exactly why the IDA/UIUC/NIU rulesets have something like "if all else fails, try the TCP mailer - there might be an MX record". (The documentation is arguable bad, but the idea behind it is solid). If you send such a message to the TCP mailer, and there is a nameserver lookup failure, the message will be requeued for later trial. If the TCP mailer says 'Unknown host', it says this because the nameserver lookup was "successful" in returning NXDOMAIN, thus documenting that the name is not known to the nameservers. The soft failure you are seeing gives a nameserver return indicating server failure, and this triggers the requeuing. -- =*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*= Neil W. Rickert, Computer Science <rickert@cs.niu.edu> Northern Illinois Univ. DeKalb, IL 60115 +1-815-753-6940