This may or may not be related to
BCLOUD-8817: all of the attached messages except for “11-succeeded-web.eml” were ignored by issue tracker. All except “10-failed-web.eml” were send from yandex.mail smartphone app. They have pretty much nothing in common except for the app and the sender (excluding some messages which were send from alternative yandex domain).
10-failed-web probably failed because it did not have quote and thus belongs to
BCLOUD-8817. But maybe it the result of the difference in quotes left by yandex.mail and web interface. In any case I do not see why certain quote format and its presence must be a requirement, github works fine with this app.