The MIME type of the message.
This is parsed from the Content-Type header in headers. It contains only
the MIME type, without any Content-Type parameters.
If headers doesn't have a Content-Type header, this will be null.
The MIME type of the message.
This is parsed from the Content-Type header in headers. It contains only
the MIME type, without any Content-Type parameters.
If headers doesn't have a Content-Type header, this will be null.