Multiple delivering problem

I am managing the mail system.
The system is a mechanism of delivering mail from an internal server
to a server on DMZ
and delivering it outside.
The trouble occurred by this system when the e-mail magazine was
delivered.
The server on DMZ sent two or more mails(empty or broken header ...)
outside
though only one mail was delivered from an internal server to the
server on DMZ.
Memory of the server on DMZ was insufficient at that time (from a
resource monitoring log).
What is the presumed cause?


■OS:solaris9

■version：sendmail-8.12.11

■mail system

e-mail magazine app(Tomcat)
↓
internal SendMail
↓
DMZ SendMail
↓
ybbmx1.mail.yahoo.co.jp

■syslog


Internal server

・stcsmi001

Oct 23 19:13:05 stcsmi001 sendmail[8451]: [ID 801593 mail.info]
l9NAD4Nm008451:
from=, size=9742, class=0, nrcpts=1, msgid=<200
71023.1920330640.******@***.co.jp>, proto=ESMTP, daemon=Dae
mon0, relay=localhost [127.0.0.1]

Oct 23 19:23:51 stcsmi001 sendmail[8509]: [ID 801593 mail.info]
l9NAD4Nm008451:
to=<######@###.ne.jp>, delay=00:10:47, xdelay=00:10:46, mailer=smtp,
pri=129742
, relay=[172.21.24.112] [172.21.24.112], dsn=4.0.0, stat=Deferred:
Connection reset by [172.21.24.112]

Oct 23 19:58:14 stcsmi001 sendmail[29163]: [ID 801593 mail.info]
l9NAD4Nm008451:
to=<######@###.ne.jp>, delay=00:45:10, xdelay=00:00:00, mailer=smtp,
pri=21974
2, relay=[172.21.24.112], dsn=4.0.0, stat=Deferred: Connection refused
by [172.21.24.112]

Oct 23 20:35:14 stcsmi001 sendmail[24175]: [ID 801593 mail.info]
l9NAD4Nm008451:
to=<######@###.ne.jp>, delay=01:22:10, xdelay=00:00:00, mailer=smtp,
pri=30974
2, relay=[172.21.24.112], dsn=4.0.0, stat=Deferred: Connection refused
by [172.21.24.112]

Oct 23 22:33:14 stcsmi001 sendmail[116]: [ID 801593 mail.info]
l9NAD4Nm008451: t
o=<######@###.ne.jp>, delay=03:20:10, xdelay=00:00:10, mailer=smtp,
pri=399742,
relay=[172.22.24.112] [172.22.24.112], dsn=2.0.0, stat=Sent
(l9NDBYWu005715 Message accepted for delivery)
※It fails in the transmission three times, and it succeeds in the
fourth times.


The server on DMZ

・socsme001
Oct 23 19:25:11 socsme001 sendmail[29310]: [ID 801593 mail.info]
l9NAIntu029310:
from=, size=9856, class=0, nrcpts=1, msgid=<20
071023.1920330640.******@***.co.jp>, proto=ESMTP, daemon=MT
A-v4, relay=stcsmi001.XXX.XX.co.jp [172.22.250.36]
Oct 23 19:53:48 socsme001 sendmail[3555]: [ID 801593 mail.info]
l9NAIntu029310:
to=<######@###.ne.jp>, delay=00:34:57, xdelay=00:00:01, mailer=esmtp,
pri=12985
6, relay=ybbmx1.mail.yahoo.co.jp. [203.216.243.175], dsn=2.0.0,
stat=Sent (ok dirdel)
※The delivery is completed though it failed.

・socsme002
Oct 23 19:20:44 socsme002 sendmail[12795]: [ID 801593 mail.info]
l9NADlDu012795:
from=, size=9856, class=0, nrcpts=1, msgid=<20
071023.1920330640.******@***.co.jp>, proto=ESMTP, daemon=MT
A-v4, relay=stcsmi001.XXX.XX.co.jp [172.22.250.36]
Oct 23 19:44:33 socsme002 sendmail[19627]: [ID 801593 mail.info]
l9NADlDu012795:
to=<######@###.ne.jp>, delay=00:30:45, xdelay=00:00:01, mailer=esmtp,
pri=1298
56, relay=ybbmx3.mail.yahoo.co.jp. [203.216.243.174], dsn=2.0.0,
stat=Sent (ok dirdel)
※The delivery is completed though it failed.

・stcsme001
Oct 23 22:33:08 stcsme001 sendmail[5715]: [ID 801593 mail.info]
l9NDBYWu005715:
from=, size=9856, class=0, nrcpts=1, msgid=<200
71023.1920330640.******@***.co.jp>, proto=ESMTP, daemon=MTA
-v4, relay=stcsmi001.XXX.XX.co.jp [172.22.250.36]
Oct 23 22:33:14 stcsme001 sendmail[11872]: [ID 801593 mail.info]
l9NDBYWu005715:
to=<######@###.ne.jp>, delay=00:00:08, xdelay=00:00:00, mailer=esmtp,
pri=1298
56, relay=ybbmx1.mail.yahoo.co.jp. [124.147.39.206], dsn=2.0.0,
stat=Sent (ok dirdel)
※E-mail is delivered without trouble.