Network Delay

[Roman Gelfand <rgelfand2@gmail.com>]

Looking at the tcp stream, below, of a smtp conversation, it appears
there is 5 second delay before the actual smtp conversation begins.
Is this normal behavior.  If not, any ideas what/where specifically,
in networking, I should be troubleshooting?  No change was done to the
server or any other machines on the network.  This started happening
all of a sudden.

15047 02:57:33.441270000 192.168.0.209 192.168.0.239 TCP 66 54398 >
smtp [SYN] Seq=0 Win=8192 Len=0 MSS=1460 WS=4 SACK_PERM=1
15048 02:57:33.441494000 192.168.0.239 192.168.0.209 TCP 66 smtp >
54398 [SYN, ACK] Seq=0 Ack=1 Win=14600 Len=0 MSS=1460 SACK_PERM=1
WS=16
15049 02:57:33.441515000 192.168.0.209 192.168.0.239 TCP 54 54398 >
smtp [ACK] Seq=1 Ack=1 Win=65700 Len=0
15237 02:57:38.461112000 192.168.0.239 192.168.0.209 SMTP 97 S: 220
pmx1.mydomain.biz ESMTP Postfix

Thanks in advance