Content-ID (cid) for SendMail nodes

The idea is:

SendMail, GMail Send-Feature and others should support a Content-ID for attachments. This can be optionally set for each attachment.

My use case:

I want to send an E-Mail with an attachment (image). This is image should be embedded within an IMG-Tag and shown in the E-Mail.

I think it would be beneficial to add this because:

Attached Images can be rendered within HTML-E-Mails. Inline Base64 does not work with GMail.

Any resources to support this?

See CID Using attachments – Nodemailer

Are you willing to work on this?

Sorry, not a programmer anymore.