Mailspring is removing custom headers provided from the sender once I reply. I found it when replying to issues generated via Gitlab: we have gitlab configured to allow developers reply to emails and generate comments on issues. Gitlab controls the thread via two custom headers:
Thread-Topic: repo-name | issue title (#225) Thread-Index: FOmNZclVgug6MVht1qPdoXk9XWrm4w==
As Mailspring destroys these headers on doing a reply, gitlab is not able to recognize the email sent.
I suppose this will happen with any header related logic regarding emails comunication.
Is there any option to prevent removing the headers?
(Originally posted by ribanez7 on GitHub.)