Having admin'd an Internet server since 1993 and also writing my own custom email server, I've had a lot of experience with email problems.



Very true. The first thing to look at is the logs closest to the origin and see how far the message got.

First, check that the two clients (of the one that works and the one that doesn't) are using the same outbound SMTP server. If they aren't, maybe they should be?

If they are using the same outbound SMTP server, check the logs on that SMTP server and see how they differ for the two messages. Or, if no difference, verify that both messages were successfully handed off to the next SMTP server in the routing. If they were both handed off to the next SMTP server, you need to again check the logs on that SMTP server. And so forth, until you find the point of failure.

If that doesn't give the answer (or the log doesn't even show any connection from the failing client), go to the failing machine and trying telnetting into the outbound SMTP server and issuing the SMTP commands manually on the keyboard. This requires knowledge of SMTP protocol but it is not terribly complicated. If there is a failure at this point, it should be clear when you are in telnet mode issuing the commands manually.

I agree with the previous post, though. This is something that has to be traced starting at FTDI. Only once they can produce logs that show that the message was handed off to a server outside of their control are they off the hook.

Regards,
Craig Steiner