timed out while sending message body

Hi everybody!
I have a problem sending mails, but it's few times in a week.

#mailq
-Queue ID- --Size-- ----Arrival Time---- -Sender/Recipient-------
522916BFB 764450 Thu Mar 13 15:01:34 <localuser>@<mydomain>
(conversation with <remotemx.domain>[200.72.206.xx] timed out while
sending message body)
mespinosa@edm.cl

78DA66BBD 3321446 Thu Mar 13 13:04:30 <localuser>@<mydomain>
(conversation with <remotemx.domain>[163.247.xx.xx] timed out while
sending message body)
<remoteuser@remdomain1>

9BEEA6BC2 7706145 Thu Mar 13 13:02:22 <localuser>@<mydomain>
(conversation with <remotemx.domain>[163.247.xx.xy] timed out while
sending message body)
<remoteuser@remdomain1>
(conversation with <remotemx.domain>[163.247.xx.xz] timed out while
sending message body)
<remoteuser@remdomain2>


MTU is 1000 (I started with 1500 and going down )

# postconf | grep smtp_data
smtp_data_done_timeout = 650s
smtp_data_init_timeout = 120s
smtp_data_xfer_timeout = 220s

This is a SLES9 SP3, and with IMSS (TrendMicro) spamfilter.


Can anybody help me please?