In general case partial file does not contains content of message (it contains only headers) so we are investigating this issue in detail and have logged it with ID “EMAILNET-39238” for further investigation.
Moreover, it is requested to kindly share more partial files if available with you.
I like to share that the concerned EMAILNET-39238 issue is going to get resolved in upcoming Aspose.Email for .NET 19.2. We will share the good news with you as soon as the issue will be fixed.