Disclaimer: I would not trust Netscape to correctly display Mime attachments using "view source". (What version of Netscape, and on what platform, are you using?)

Have you tried verifying the correct presentation of your attachments using another MUA? Because I assume what you are wanting to verify is that the recipients of your complete mail messages will see the the text of the main part of your message, and the fact that there are several "mimed" attachments, each of which they can view or deal with as they wish. If the message appears to be structured correctly using a common MUA, then you have what you want.

For example, send it to a dummy hotmail account, and look at your message that way. You can set the hotmail options to display the complete mail headers in full detail, including all mime stuff.