Hello :slight_smile:
I’ve attached a sample eml:
Dim xx As New Email.MailMessage
xx.Save(“d:\a.eml”)
a.zip (170 Bytes)
and email detect file format detects it as mhtml.
since you set:
X-Unsent: 1
by default, is t…...and MHT are both RFC 5322 / MIME containers, so DetectFileFormat...DetectFileFormat relies on heuristics (MIME structure, Content-Type , etc...