Hello,
Can you please be kind and try to use
FileFormatUtil.DetectFileFormat(fileStream).FileFormatType
To detect the attached 3 files?
They are binary libraries detected as Mht!
** Any non printable characters before headers must return false immediately **
If anyone uses DetectFileFormat instead of file extension to open/load files into Aspose Email, such errors put them in hard situations 
Thanks.
Mht.zip (7.2 KB)
Hello @australian.dev.nerds,
Thank you for bringing this to our attention. We will investigate this case.
@australian.dev.nerds
We have opened the following new ticket(s) in our internal issue tracking system and will deliver their fixes according to the terms mentioned in Free Support Policies.
Issue ID(s): EMAILNET-41790
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