Why does iPhone eMail signature go out as an attachment?

Question

I am building an iPhone application that generates an email with an attachment. The eMail message window pops up showing the body text and attachment followed by the default "Sent from my iPhone" signature text.

Everything seems perfectly ok, except when the message is received by the recipient the signature "Send from my iPhone" has been converted into a text attachment instead of remaining as the last line of the body. What gives?

Update: It seems that it's only Outlook that exhibits this behaviour. When I view the message in iPad Mail the signature does show as body text, not an attachment.

Answer 1

How does the email view in other applications, such as Apple Mail, Eudora, Lotus Notes, Thunderbird, etc ?

I'm suspecting that it's to do with Outlook's anal attempts to "protect the user experience", the same as it does if you email an EXE file (won't let the recipient open it).