That’s an old freeware utility, I haven’t seen it in a while.
I would start with the basics:
Insure the subsystem it’s designated to run in is active.
Verify the jobq is not on hold and is attached.
WRKACTJOB to see if the OPRMONITOR job is running.
Check if the SMTP server is active.
It uses SNDDST to send the message, make sure the dstq is not on hold.
DSPDSTLOG and review for any errors.
If all that checks out, manually SNDDST and follow it thru.
IF your DASD % usage hit the threshold you’ll need to make sure you’re back under your monitor limits before you try to restart the SMTP service. SMTP will turnoff whenever DASD limits are exceeded.