[Mimedefang] mimedefang and incoming facebook email

[cc]

Hi,

I'm using Sendmail with mimedefang.

Recently a co-worker was having trouble with a company facebook
account and got Facebook to send her a 'reset-password' email.

When she received it, it came only with the following message:

    This message contains a rich-text HTML portion. Consult
    your mail client's documentation for information on how to
    view it.

After I disabled mimedefang, the e-mail went through properly.

My question is, how come I couldn't find "This message ..."
in mimedefang's sources?

I know that mimedefang alters e-mails.  I'm just curious
as to where this message came from if I can't find it
in the mimedefang sources.  I guess, ergo, it isn't mimedefang;
but, re-enabling it gives me that message.

Any clarifications appreciated.

Edmund