SEO

Hello,
I recently took over a network that includes a SCO server that runs
customized software; I am not able to install patches and updates at
will. This server also functions as our mail server. (UnixWare 7.1.1,
SendMail 8.12.2)

While investigating the reason why e-mails to certain domains wouldn't
go through (blacklisting is not a problem), I have found that when the
server sends the message body in fragmented packets, the message is not
delivered successfully. All of the fragmented packets have an offset
of 0 - I had expected the second packet's offset to be 185, and
so-forth.

First, if anyone can think of a way to fix the offset problem, that
would be great. The second-best solution would be to prevent the
server from fragmenting packets.

Finding the second-best solution is complicated a bit by the fact that
ifconfig is already setting the "full-size frames" to 1 and inconfig is
setting the "in_fullsize" variable to 1.

Below is the ifconfig for the adapter and an export of the first three
packets of a message body (addresses are faked to protect the guilty).
I would greatly appreciate any help you can offer - Thanks in advance!
Brian

-------------------------
ifconfig net0
net0: flags=4043<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.1.1 netmask ffffff00 broadcast 192.168.1.255
inet/perf: recv size: 24576; send size: 24576; full-size frames: 1
inet/options: rfc1323
---------------------------
Ethereal Logs {all of my edits are in braces}

No. Time Source Destination Protocol Info
16 0.291 {US} {THEM} IP Fragmented IP protocol (proto=TCP 0x06,
off=0)

Frame 16 (1514 bytes on wire, 1514 bytes captured)
Arrival Time: Dec 27, 2005 21:29:38.677972000
Time delta from previous packet: 0.003267000 seconds
Time since reference or first frame: 0.291503000 seconds
Frame Number: 16
Packet Length: 1514 bytes
Capture Length: 1514 bytes
Protocols in frame: eth:ip:data
Ethernet II, Src: {Server MAC}, Dst: {Firewall MAC}
Destination: {Firewall MAC}
Source: {Server MAC}
Type: IP (0x0800)
Internet Protocol, Src: {US}, Dst: {THEM}
Version: 4
Header length: 20 bytes
Differentiated Services Field: 0x00 (DSCP 0x00: Default; ECN: 0x00)
0000 00.. = Differentiated Services Codepoint: Default (0x00)
.... ..0. = ECN-Capable Transport (ECT): 0
.... ...0 = ECN-CE: 0
Total Length: 1500
Identification: 0xf6a7 (63143)
Flags: 0x02 (More Fragments)
0... = Reserved bit: Not set
.0.. = Don't fragment: Not set
..1. = More fragments: Set
Fragment offset: 0
Time to live: 64
Protocol: TCP (0x06)
Header checksum: 0x5be0 [correct]
Good: True
Bad : False
Source: {US}
Destination: {THEM}
Data (1480 bytes) {actual data omitted}


No. Time Source Destination Protocol Info
18 1.284 {US} {THEM} IP Fragmented IP protocol (proto=TCP 0x06,
off=0)

{snip - all info except time duplicate of first packet}
Internet Protocol, Src: {US}, Dst: {THEM}
Version: 4
Header length: 20 bytes
Differentiated Services Field: 0x00 (DSCP 0x00: Default; ECN: 0x00)
0000 00.. = Differentiated Services Codepoint: Default (0x00)
.... ..0. = ECN-Capable Transport (ECT): 0
.... ...0 = ECN-CE: 0
Total Length: 1500
Identification: 0xf6a8 (63144)
Flags: 0x02 (More Fragments)
0... = Reserved bit: Not set
.0.. = Don't fragment: Not set
..1. = More fragments: Set
Fragment offset: 0
Time to live: 64
Protocol: TCP (0x06)
Header checksum: 0x5bdf [correct]
Good: True
Bad : False
Source: {US}
Destination: {THEM}


No. Time Source Destination Protocol Info
20 2.284 {US} {THEM} IP Fragmented IP protocol (proto=TCP 0x06,
off=0)

{snip - all info except time duplicate of first packet}
Internet Protocol, Src: {US}, Dst: {THEM}
Version: 4
Header length: 20 bytes
Differentiated Services Field: 0x00 (DSCP 0x00: Default; ECN: 0x00)
0000 00.. = Differentiated Services Codepoint: Default (0x00)
.... ..0. = ECN-Capable Transport (ECT): 0
.... ...0 = ECN-CE: 0
Total Length: 1500
Identification: 0xf6a9 (63145)
Flags: 0x02 (More Fragments)
0... = Reserved bit: Not set
.0.. = Don't fragment: Not set
..1. = More fragments: Set
Fragment offset: 0
Time to live: 64
Protocol: TCP (0x06)
Header checksum: 0x5bde [correct]
Good: True
Bad : False
Source: {US}
Destination: {THEM}
Data (1480 bytes) {actual data omitted}