4.4.2 error

[Cybersync]

This is my first post to list so I hope I'm doing it correctly. My problem is that i'm getting the Connected_to_xxx.xxx.xxx.xxx_but_connection_died._(#4.4.2) error. I've gone through the 180 messages in the archive which mention this error and most say there is a problem with the ISP. I'm happy to accept this but the problem only occurs when sending attachments. Here is a list of some of the mailservers it dies on.   MS                    IP Mailsweeper      203.42.9.21 NT Mail             203.24.77.42 Sendmail          203.26.120.3 Sendmail          203.13.168.11 Exim                195.147.246.129   The setup is the same as 8 other qmail servers I have setup without a problem. Qmail 1.0.3, RedHat 6.2, daemons supervised by ucspi-tcp-0.88 dialup 56k modem to ISP. I have dropped concurrent remote down to 2 and upped all send and smtp timeouts to see if it made any difference but it didn't. I can send small messages out ok and can receive messages with or without attachments ok. I can also telnet to the addresses ok on port 25 from the same box. There was a post previously about a throttling packet shaper causing problems when it was switching between channels but the ISP reckons they don't have anything like that. I would also like to know if there is a document that tells me how to have more of a conversation with a mailserver through telnet that just the helo and ehlo commands I have been using.   Any ideas no matter how remote would be greatly appreciated.   Craig Needs Adelaide, South Australia