[Exim] Heavy traffic

Have a problem...I have a huge mailing list (500+ people) which gets emailed nightly. At first, I figured the problem was having too many exim sessions open (since each email was a new connection to the server).

But now, I have it stream all the emails on 1 connection....it now gives errors about log failure. So far I turned off sender_verify/receiver_verify, set smtp_accept_queue_per_connection to both 999 and 0 (no effect), and turned on split_spool_directory.

What the script does is stream all the emails at once (test addresses...I have aliases a1 through a500 point to a mailbox on a remote machine)...here is the log (I removed the real domain):

--snip--
[May 31 2001 12:27:54] Start run.
[May 31 2001 12:28:29] Unexpected return code: 421 Unexpected log failure, pleas
e try later

[May 31 2001 12:28:29] Error sending mail #234 to 'a235@x'.
[May 31 2001 12:28:29] Attempting RSET after 10 second sleep...
[May 31 2001 12:28:39] RSET successful - attempting resend to 'a235@x'.
[May 31 2001 12:28:39] Unexpected return code: 421 Unexpected log failure, pleas
e try later

[May 31 2001 12:28:39] Error sending mail #234 to 'a235@x' - abo
rting send.
[May 31 2001 12:28:39] Attempting RSET after 10 second sleep...
[May 31 2001 12:28:49] Unexpected return code: 421 Unexpected log failure, pleas
e try later

[May 31 2001 12:28:49] Error sending mail #235 to 'a236@x'.
[May 31 2001 12:28:49] Attempting RSET after 10 second sleep...
[May 31 2001 12:28:59] RSET successful - attempting resend to 'a236@x'.
[May 31 2001 12:28:59] Unexpected return code: 421 Unexpected log failure, pleas
e try later

[May 31 2001 12:28:59] Error sending mail #235 to 'a236@x' - abo
rting send.
[May 31 2001 12:28:59] Attempting RSET after 10 second sleep...
[May 31 2001 12:29:09] Unexpected return code: 421 Unexpected log failure, pleas
e try later

[May 31 2001 12:29:09] Error sending mail #236 to 'a237@x'.
[May 31 2001 12:29:09] Attempting RSET after 10 second sleep...
[May 31 2001 12:29:19] RSET successful - attempting resend to 'a237@x'.
[May 31 2001 12:29:19] Unexpected return code: 421 Unexpected log failure, pleas
e try later

[May 31 2001 12:29:19] Error sending mail #236 to 'a237@x' - abo
rting send.
[May 31 2001 12:29:19] Attempting RSET after 10 second sleep...
[May 31 2001 12:29:29] Unexpected return code: 421 Unexpected log failure, pleas
e try later

[May 31 2001 12:29:29] Error sending mail #237 to 'a238@x'.
[May 31 2001 12:29:29] Attempting RSET after 10 second sleep...
[May 31 2001 12:29:39] RSET successful - attempting resend to 'a238@x'.
[May 31 2001 12:29:39] Unexpected return code: 421 Unexpected log failure, pleas
e try later

[May 31 2001 12:29:39] Error sending mail #237 to 'a238@x' - abo
rting send.
[May 31 2001 12:29:39] Attempting RSET after 10 second sleep...
[May 31 2001 12:29:49] Unexpected return code: 421 Unexpected log failure, pleas
e try later

[May 31 2001 12:29:49] RSET failure...reinitializing...
--snip--

At this point it drops the current connection and reconnects...same results.

Is there some massive load feature that I didn't read in the manual? Would it work better or be more efficient if I had it process the mailing list on the smtp server and use the stdin for exim?

Thanks...

-Sam