@qtsoft
We have investigated this issue and found that this is not a bug of Aspose.Email. For various versions of the MAC, the paths for saving partial files, their names and formats may be different, therefore it is a very difficult task to implement the general case. However, you may use the following code to correctly convert files to EML format:
var filename = Path.Combine(TestUtil.GetTestPath("EMAILNET_39219"), "80394.partial.emlx");
var lrFilename = Path.Combine(TestUtil.GetTestPath("EMAILNET_39219"), "80394.1.2.emlxpart");
var attFilename = Path.Combine(TestUtil.GetTestPath("EMAILNET_39219"), "80394.2.emlxpart");
MailMessage message = MailMessage.Load(filename, new EmlxLoadOptions());
message.LinkedResources[0].ContentStream = new MemoryStream(Convert.FromBase64String(File.ReadAllText(lrFilename)));
message.Attachments[0].ContentStream = new MemoryStream(Convert.FromBase64String(File.ReadAllText(attFilename)));
message.Save(filename + ".eml");
Moreover, please feel free to write back to us if you need additional information or you have any further queries.