Sorry you had trouble with the error code. I know we missed a few on the initial release of 9.1, but we've been catching up. I just loaded the latest PAC Control and found the on-line help for the command "Send Email" does include this:
-70 = Not enough data supplied. Check Server Information table elements.
The on-line help for the command usually has the best chance of providing a clue, especially since we sometimes re-use similar errors for different commands.
I will also make a note of that when I update the Samples & Freeware download (the sample email chart). I'll add a request that we include more info in form 1700 as well.