Finally got this to work! It seems that the nodemailer plugin has a dependency on node v 6.0.0. As soon as I changed the dependency to a compatible version the problem was solved.
Hope this helps someone else facing the same issue.
I installed emailer-sendgrid plugin by julianlam on my NodeBB versions 1.12.2 which says its compatible with this version. However, when I go to the Plugins -> Emailer (Sendgrind) and click it, the /admin/plugins/emailer-sendgrid page just loads indefinitely and never actually comes up, ever. Do you know what could cause this and some troubleshooting steps? One thing I did try is I restarted NodeBB after I installed it and logged out and logged back in. I DID NOT do a rebuild/restart though.
try to rebuild and restart sometime it solves the issues.