If the user accepts the meeting, the option appears to edit the item before sending - they are probably using this option. You can also do this using the Send Update function.

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Milly Staples [MVP - Outlook]
Post all replies to the group to keep the discussion intact. All
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After furious head scratching, Sam MacCutchan asked:
| Is it possible for attendees of meetings to update the meeting by
| either adding text or attaching files to the meeting in Outlook 2003
[quoted text clipped - 12 lines]
| I am probably missing something glaringly obvious but any help would
| be greatly appreciated.
Sam MacCutchan - 03 Oct 2007 13:05 GMT
If I selected 'Edit the response before sending' it sends an email to the
organizer with the attachment, but the attachment is not added to the meeting.
Some people have the 'Send Update' button and other's don't but I can't
figure out why.
> If the user accepts the meeting, the option appears to edit the item before sending - they are probably using this option. You can also do this using the Send Update function.
>
[quoted text clipped - 14 lines]
> | I am probably missing something glaringly obvious but any help would
> | be greatly appreciated.