Thank you for contacting Aspose support team.
We have tried to reproduce the issue using sample EML but could not succeed. Following sample code is used for testing:
MailMessage mail1 = MailMessage.Load(@"5211_4_1a_c89276fefa5213be971de324439ac.0_9563.eml",
MailMessage mail2 = MailMessage.Load(@"5221_a_44_f4115cdda38e5894465eda228dfe8.0_241103.eml",
Is it possible for you to save the original stream (fetched email from server) in a file and provide us before saving it as EML? This original data stream will help us to observe the problem and provide assistance.