Create a mime-mail message directly.

mime-mail's simpleMail function wants an HTML body, and if we just set it to the empty string, then HTML-compliant mail clients will render only that part, so that the body appears to be empty.

So, just use mime-mail's Mail type directly.
Fix from/to email bug.

Swapped them in the last update.

Also, change srcEmail -> fromEmail and dstEmail -> toEmail, it's
clearer.