trouble to connetc to random remote servers with telnet

[mbeltran at americatel.com.sv]

Hi everyone

I have a box, a FreeBSD 5.3-release whit qmail version 1.03 and the
SPAMCONTROL patch 2.3.11, all have worked fine, but since a few days i cant
connect to several random mail servers. i have a cisco gateway that hasnt
changed any config.

One of my qmail log message is this:
@4000000042a734fd0287b674 starting delivery 193941: msg 8543907 to remote
abcdefg at laprensa.hn
@4000000042a734fd0287b888 delivery 193941: deferral:
Connected_to_200.30.172.163_but_connection_died._(#4.4.2)/

I guess that I had problems with qmail. So, i try to connect manually to the
remote box, but a i got this message:
asgard1# telnet 200.30.172.163 25
Trying 200.30.172.163...
Connected to correos.laprensa.hn.
Escape character is '^]'.
Connection closed by foreign host.

The next step was to ping the remote server and i got this:
asgard1# ping 200.30.172.163
PING 200.30.172.163 (200.30.172.163): 56 data bytes
64 bytes from 200.30.172.163: icmp_seq=0 ttl=120 time=592.278 ms
64 bytes from 200.30.172.163: icmp_seq=1 ttl=120 time=598.336 ms
64 bytes from 200.30.172.163: icmp_seq=2 ttl=120 time=473.944 ms
^C
--- 200.30.172.163 ping statistics ---
4 packets transmitted, 3 packets received, 25% packet loss
round-trip min/avg/max/stddev = 473.944/554.853/598.336/57.264 ms

And then I have run tcpdump while i did telnet to the host again and the
response was:
asgard1# /usr/sbin/tcpdump -vv dst host 200.30.172.163
tcpdump: listening on bge0, link-type EN10MB (Ethernet), capture size 96
bytes
14:41:57.581161 IP (tos 0x10, ttl  64, id 29721, offset 0, flags [DF],
length: 64, bad cksum 0 (->e8b7)!) asgard1.americatelsal.com.50523 >
correos.laprensa.hn.smtp: S [bad tcp cksum de09 (->4972)!]
2831888326:2831888326(0) win 65535 <mss 1460,nop,nop,sackOK,nop,wscale
1,nop,nop,timestamp 1002910953 0>
14:41:58.589763 IP (tos 0x10, ttl  64, id 29929, offset 0, flags [DF],
length: 52, bad cksum 0 (->e7f3)!) asgard1.americatelsal.com.50523 >
correos.laprensa.hn.smtp: . [bad tcp cksum ddfd (->3a17)!]
2831888327:2831888327(0) ack 2488154443 win 33304 <nop,nop,timestamp
1002911054 0>
14:41:59.770450 IP (tos 0x10, ttl  64, id 30131, offset 0, flags [DF],
length: 52, bad cksum 0 (->e729)!) asgard1.americatelsal.com.50523 >
correos.laprensa.hn.smtp: . [bad tcp cksum ddfd (->29f2)!] 0:0(0) ack 2 win
33304 <nop,nop,timestamp 1002911172 9178914>
14:41:59.770565 IP (tos 0x10, ttl  64, id 30132, offset 0, flags [DF],
length: 52, bad cksum 0 (->e728)!) asgard1.americatelsal.com.50523 >
correos.laprensa.hn.smtp: F [bad tcp cksum ddfd (->29f1)!] 0:0(0) ack 2 win
33304 <nop,nop,timestamp 1002911172 9178914>

Look at the "bad tcp cksum" message, is the only thing that i look strange. 

But is very extrange that I can connect with telnet on 80 port to the same
server, look at following lines:
asgard1# telnet 200.30.172.163 80
Trying 200.30.172.163...
Connected to correos.laprensa.hn.
Escape character is '^]'.
quit
HTTP/1.1 400 Bad Request ( The data is invalid.  )
Connection: close
Pragma: no-cache
Cache-Control: no-cache
Content-Type: text/html
.
.
.... etc


If i tried to connect using others mailservers running or not running qmail
on the same
subnet, i got this successful message:
[root at thor mbeltran]# telnet 200.30.172.163 25
Trying 200.30.172.163...
Connected to correos.laprensa.hn (200.30.172.163).
Escape character is '^]'.
220 laprensa.hn ESMTP MDaemon 6.8.4; Wed, 08 Jun 2005 14:41:16 -0600
quit
221 See ya in cyberspace
Connection closed by foreign host.


I really dont know what thing should i do for solve this problem. Any
suggestions?
 
Thanks in advance and regards.
 
Mario.