I just had yet another email rejected by hughes.net
Incredably, it was rejected because it had the Subject: line that read "To start a brawl" which, when I changed the Subject: line to "The Preserve," hughes.net's mailer accepted the email and sent it on its way. Frankly I cannot imagine what is offensive or spam-like in "To start a brawl."
I will look for the work-arounds you have mentioned.
How confident are you that Free SMTP Server is not malicious? Could it be sending email, or other information, that you are not aware of?