You don't pay for Framagit, because it is funded by donations to Framasoft. Our not-for-profit needs any support you can afford: support.framasoft.org.
Framagit est gratuit car il est financé par les dons à Framasoft. Notre association a besoin de votre soutien sur soutenir.framasoft.org.
Also adds a script that can be used as a sendmail executable for manual testing purposes.
Credits to @X-dark for reporting the issue and finding the root cause.