Once the command completes, there should be a trace file (and possible other files) in the IFS that can assist with debugging.
The file you will want to either examine, or forward to me for help, is the following:
Where xxxx is a sequential and unique email ID. If you are on an older version of MAILTOOL then the file will simply be named /tmp/mailtoolsmtp.txt (and you should think about downloading and updating to the latest version(s) of any software of ours you have installed. It's free or any licensed partition!).
You can either transfer the file to your PC to forward to me using Operations Naviator, Windows Explorer (if you have NetServer and up running and a share to the /tmp directory), or FTP.
This file will contain a full trace of the communications between your IBM i and the mail router you are using.