Currently it is possible to have e-mails as inputs or outputs of flows.
Some headers can be set directly, like To and CC, but not all: specifically, In-Reply-To and References should be updated for email threading to work as expected.
This would allow for flows where an email by Node-RED can be clearly marked as a reply to the email that initially triggered the flow.
An easy way of implementing this is to add those fields to the existing nodemailer interface, as it implements them already.
great - we look forwards to the pull request.
Great - that was quick 
There wasn't much work to do!
I hope it is useful to others too.
I assume you have tested it and are happy with it now ?
Yes!
The messages correctly thread after setting these headers to the Message-Id of the original message. And setting the subject to "Re: [original subject]".
It was really just propagating the headers to the underlying library.
The version bump to 1.5.0 changes the dependency mailparser-mit to mailparser. This works if mailparser-mit happens to be installed but fails otherwise.
