OK, if you check the time delivery starts, and the time the error occurs, you'll notice that it is always 5 minutes, which is the fixed delivery intervall AsyncOS is set to. Most likely the remote host is lacking bandwith, lthough the file here is only 130k, so it might also be an MTU issue on their end, considering your delivery with other hosts works without problem. I suggest that you set up a domain debug log with the domain in question, and check how far delivery goes. If the log only shows the message headers, and stops at the "data" section, then an MTU problem is the cause, so thei'd need to fix their firewall to allow ICMP path discovery trough. If you see data transmitted after the header part, then their bandwith is too slow. In this case it sometimes helps to configure a destination control entry for that domain, which limits the number of concurrent connections to one, or two at most - even if that sounds like a drastic change (however, 5 minutes to get 130k trough...not much of a choice I'd say).
Hope that helps,
Andreas
