A mailing of that size is likely to be blocked by your mail server anyway.
Better to do a mail merge to individual messages. Select all the contacts in
the category, then choose Tools | Mail Merge and proceed from there.

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Sue Mosher, Outlook MVP
Author of
Microsoft Outlook Programming - Jumpstart for
Administrators, Power Users, and Developers
http://www.outlookcode.com/jumpstart.aspx
> When you use categories to do mass mailings (using the By
> Category view, then choosing Actions | New Message to
[quoted text clipped - 5 lines]
> If the problem persists, restart Outlook." Or is it a
> memory limitation on my computer?