I got this error while setting up FatFreeCRM on heroku and got this error, when I tried testing sending password reminder email.
If testing the same using rails console, everything seems to be working fine.
heroku run rails console
me = User.first
It turns out to be a heroku specific issue, you need to set HEROKU to true
heroku config add HEROKU=true
and everything works like a charm
Hope, it helps someone.