Arun K. Khan wrote:

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On Thu, 2006-07-13 at 12:22 +0530, Amish Mehta wrote: I have a customer who uses linux (RH9) and sendmail as outgoing SMTP server.

There is a strange problem. SMTP server delivers e-mails everywhere around the world except the domains in China. Most of times sendmail gives errors that "lookup failed" and returns e-mails after 5 days of trying.

The NS machines must be down/unreachable or the NS entries @ the Domain registrar may not be up to date. Have you tried to resolve MX record manually?

Yes MX resolves... but I tried debug mode with -d<N.NN>. Sendmail fails at lookup of AAAA record (which it does before doing MX). But sometimes it DOES succeed and mails get delivered too. But most of times it does not succeed. So I dont know why? It fails with both local as well as iqara DNS. I also updated 'root' zone but problem still exists.

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For some domains it states "invalid sender xyz@vsnl.net" and keeps trying for 5days.

I know you are using sendmail but ... Are you trying to send the messages directly from your own SMTP server i.s.o. of the ISP's SMTP relay (smart host)? If so, the receiving MTAs may be configured to reject messages from IPs that do not match with vsnl.net's SMTP host(s).

Well I cant use VSNL as smart host as customer uses iqara network and VSNL allows only its own network to use its own SMTP. So their is no smart host, its directly delivery. But right now I am interested in solving "lookup failure" problem first not this one. You may be right for this "invalid sender" problem.

Thanks.

Amish.