MIME Boundary field meaning & decoding in email header(mail.com web client)

Dear All
As we know some important information can be found in MIME Boundary field in email headers. Such as the one described in this nice & interesting link (Dates in Hiding Part 2 — Gmail MIME Boundary Timestamps]
Do you have any idea about MIME Boundary field & method of decoding it for an email sending from mail.com Webmail client (Through HTTP connection with mail server)
Regards,