Are you saying that when you send "all 14" tests to yourself, then open them in Horde, they show the "from" address you entered in mailsploit?
I ran the test on my server and didn't receive any of the tests - presumably my qpsmtpd or firewall settings blocked the sending mail server (or it takes longer than 25 minutes for mailsploit to get around to sending its messages).
If you provide the IP address that delivered the messages to your SME server I will try to figure out why the delivery to my system failed.
I have found no connection attempts from the mailsploit.com MX ips (198.54.122.215, 198.54.122.213) or A ips (104.25.35.16), no new email in my Inbox, and no record of 'mailsploit' or 'potus' in my qpsmtpd log files.