Hi, I'm new to this list - might as well introduce myself. I'm a system administrator in the line of MS products, looking back on a career of 10 years now. I live in Germany. Any other questions feel free to ask :) To the topic: I experience a strange issue when sending mails that contain an attachment. I send mails via smarthost, and my exchange 2000 sp3 is behind isa server. With increasing attachment size, the probability of successful delivery decreases, e.g. sending a 8 mb file never works, 100 byte always works, and everything in between results in the email being delivered multiple times, either sitting in the outbound queue forever or getting removed from the queue eventually. With the help of my ISP I found out that on the smart host side an interruption of communications is logged. I found no errors in my logfiles however. I think I can rule out ISA as a culprit as well. Hopefully one of you has a good idea. I'm not really a troubleshoort as it comes to exchange, so I'd be grateful for any directives in that respect. Thanks Mark