About the time of the auto update of thunderbird 45.3.0 my host, hostmonster can not send out emails created in thunderbird. I see the email in hostmonster in the "Sent" box of roundcube(email client) but it doesn't go to the recipient. I've spent dozens of hours on the phone with hostmonster and they say it's being flagged as spam and not being sent out. I can send mail out from roundcube ok.

I'm going wacky trying to figure out how to fix this.