Sudden slowness to respond to mail

[rob]

Not sure why but around 1:30pm yesterday, our Nagios server started complaining that it
could not connect via SMTP to either of our MailScanner servers.  I checked and we could
get mail back and forth from places like yahoo, gmail, etc.  Upon checking the logs, we
are getting a flood of this:

Jan  9 06:12:08 mail1 sendmail[22707]: l09CBX6l022707: arm180.bigfootinteractive.com
[206.132.3.180] did not issue MAIL/EXPN/VRFY/ETRN during connection to MTA
Jan  9 06:12:31 mail1 sendmail[22709]: l09CBtI0022709:
airspan-218-44.33.radom.pilicka.pl [82.197.44.218] did not issue MAIL/EXPN/VRFY/ETRN
during connection to MTA
Jan  9 06:12:34 mail1 sendmail[22715]: l09CBxwC022715: e176093214.adsl.alicedsl.de
[85.176.93.214] did not issue MAIL/EXPN/VRFY/ETRN during connection to MTA
Jan  9 06:12:53 mail1 sendmail[22727]: l09CCMuB022727: jean.fleetone.com [172.16.20.185]
did not issue MAIL/EXPN/VRFY/ETRN during connection to MTA
Jan  9 06:13:24 mail1 sendmail[22731]: l09CCnaI022731: avh179.neoplus.adsl.tpnet.pl
[83.27.41.179] did not issue MAIL/EXPN/VRFY/ETRN during connection to MTA
Jan  9 06:13:38 mail1 sendmail[22735]: l09CD3H9022735: sv25pub.verizon.net
[206.46.252.161] did not issue MAIL/EXPN/VRFY/ETRN during connection to MTA
Jan  9 06:13:57 mail1 sendmail[22742]: l09CDMxn022742: [59.39.93.106] did not issue
MAIL/EXPN/VRFY/ETRN during connection to MTA
Jan  9 06:14:10 mail1 sendmail[22744]: l09CDZG5022744: mailer204.ftl.sportsline.com
[64.30.226.39] did not issue MAIL/EXPN/VRFY/ETRN during connection to MTA
Jan  9 06:14:32 mail1 sendmail[22749]: l09CDvZU022749: srv2.worldnox.net [204.10.36.240]
did not issue MAIL/EXPN/VRFY/ETRN during connection to MTA
Jan  9 06:14:38 mail1 sendmail[22751]: l09CE3uC022751: sv25pub.verizon.net
[206.46.252.161] did not issue MAIL/EXPN/VRFY/ETRN during connection to MTA


I can see where sendmail is waiting though for a connect:

[root at maryann mqueue]# ps -ef | grep sendmail
root      5324     1  0 Jan08 ?        00:00:01 sendmail: accepting connections        
                                                                        
smmsp     5329     1  0 Jan08 ?        00:00:00 sendmail: Queue runner at 00:15:00 for
/var/spool/clientmqueue
root      5335     1  0 Jan08 ?        00:00:00 sendmail: Queue runner at 00:15:00 for
/var/spool/mqueue
root     21991  5324  0 05:38 ?        00:00:00 sendmail: server [211.203.47.134] cmd
read                                                                      
root     22872  5324  0 06:21 ?        00:00:00 sendmail: startup with
88-106-220-38.dynamic.dsl.as9105.com                                                     
root     22873  5324  0 06:21 ?        00:00:00 sendmail: startup with
dsl.dynamic859769199.ttnet.net.tr                                                        
root     22875  5324  0 06:21 ?        00:00:00 sendmail: startup with server.8disc.net
                                                                        
root     22879  1468  0 06:21 pts/0    00:00:00 grep sendmail

In doing a telnet to port 25 on each server, it is taking up to 35 seconds for sendmail
to respond on each box.  One server is CentOS 3.6 while the other is CentOS 4.4. 

sendmail-8.12.11-4.RHEL3.6
sendmail-8.13.1-3.RHEL4.5

What would cause the sudden slowness of the response?  I am not running a greet pause in
sendmail.

Thanks in advance

Rob