I have a Hostgator shared hosting/domain account that I use as a play thing.
I have spent a few days off and on trying to use my email server as the sending server, to no avail. I could send emails only to my own server, no further.
There is a "name" config option (in Nodemailer) that seems to require setting to the name of the sending account. I don't believe this option can be set in msg.envelope, or anywhere else currently, but happy to be shown otherwise.
If there is currently no way for this option to be used, what is required to add it? A PR I'm guessing?
Long Version ...
After searching far and wide for an answer I finally came across this post from someone in my exact same situation while attempting to use Nodemailer, https://stackoverflow.com/questions/56289063/nodemailor-cant-sending-emails-on-cross-domains
He added the Nodemailer connection option of "name" (https://nodemailer.com/smtp/#connection-options) and set it to hostgator. Voila!
I bumbled my way through forking the email node and added the name connection option, and Voila! as well. All emails being sent as expected.