dns config issue

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dns config issue

Postby info » Mon Apr 30, 2007 11:07 pm

We had a slowdown caused by a DNS server configuration issue. Things are back to normal and the queues are pretty much cleared now.
info
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Postby josh » Mon Apr 30, 2007 11:19 pm

For those of you who are curious:

1) to help ward off the DOS attack (still happening, but maybe abated a bit), we started using blocklists that target only virus-infected computers -- CBL has one

2) since our volume is kinda high, we had to run a special RBLDNS daemon locally (and periodically rsynch the zone files for it). We did this by running it on a non-standard port and forwarding requests from our main bind9 daemon - a standard technique

3) the bind9 daemon was swelling with cached entries from the forwarding (or at least it sure seemed that way), which was hurting performance, so we turned off caching. That worked.

4) then it stopped working, maybe due to a software update to the bind9 server.

5) blugghhhh - unresolved queries, slow service, you know the rest

6) turned back on caching in a controlled way (also lost one of the blocklists because it stopped operating) - happy again.
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Warning: could not send message for past 4 hours

Postby ScottF4 » Tue May 01, 2007 6:52 am

Is this still a problem or is all the mail I'm getting with "Warning: could not send message for past 4 hours" caused by something else? (If the email can't get through how come I get the bounce message?)

"The original message was received at Mon, 30 Apr 2007 11:12:16 GMT
from localhost.localdomain [127.0.0.1]

----- Transcript of session follows -----
... while talking to zathras2.eyecominc.com.:
>>> DATA
<<< 451 4.1.0 Sorry, I could not verify that recipient (internal temporary error).
<MAILER-DAEMON@zathras2.eyecominc.com>... Deferred: 451 4.1.0 Sorry, I could not verify that recipient (internal temporary error).
<<< 503 5.5.1 You must send RCPT TO: first
Warning: message still undelivered after 4 hours
Will keep trying until message is 5 days old

Final-Recipient: RFC822; MAILER-DAEMON@zathras2.eyecominc.com
Action: delayed
Status: 4.1.0
Remote-MTA: DNS; zathras2.eyecominc.com
Diagnostic-Code: SMTP; 451 4.1.0 Sorry, I could not verify that recipient (internal temporary error).
Last-Attempt-Date: Mon, 30 Apr 2007 15:50:47 GMT"

I've gotten at least 15 of these on 10 different addresses.

Scott
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Postby SysKoll » Tue May 01, 2007 1:15 pm

Scott,

If these are marked "temporary errors", they will be resent automatically. I got a few temp error warnings too and these finally went through (I know because these emails were responded to).
-- SysKoll
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Postby josh » Sun May 06, 2007 5:09 am

We always bust loose a bunch of stale error messages when we clear the queue after getting things back to normal -- likely that's what those were.
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