Hello,
First of all whether an attached file Views in Place, or Views as Icon while Composing, it will have absolutely NO impact on the recipient. What happens with an attachment will totally depend on their email client and whether it supports View in Place (also called Inline View).
With Mail 2.x, the exception to this can occur when you compose in Rich Text Format, and use two or more different fonts, and attach a file. This happens because the RTF in this case in converted to HTML, and it is the HTML that involves the attachment in such a way as to be problematic to certain email clients -- notably Outlook and Outlook Express. You can see this conversion if you open any such message you have sent, click on View in the menubar, place the cursor on Message and choose Raw Source.
Send to these people using only Plain Text Format, and if using a Signature (frequently the source of a second font) either do not use, or make sure the Signature is also in Plain Text. For good measure, place all attachments after any Signature.
Btw, if you look at any message, with attachment, that is sent using RTF and only ONE font, you will see that Mail converts the RTF to Plain Text on its own, but cannot do that when more than one font is employed.
Ernie