E-mail headers can be fun too. For example, Facebook e-mails up to this day contain:
X-Mailer: ZuckMail [version 1.00]
The X-Mailer header traditionally indicates the mail client that was used to send the e-mail.
Want to check if your friend who has "Sent from my iPhone" was really using an iPhone? Just look for "X-Mailer: iPhone Mail" (Of course, these headers can be arbitrarily set by a client, so this is not meant to be a definitive check.)
X-Mailer: ZuckMail [version 1.00]
The X-Mailer header traditionally indicates the mail client that was used to send the e-mail.
Want to check if your friend who has "Sent from my iPhone" was really using an iPhone? Just look for "X-Mailer: iPhone Mail" (Of course, these headers can be arbitrarily set by a client, so this is not meant to be a definitive check.)