I've added a button to both the global menu bar and application level tool
bar. They appear perfectly in IE, but not in Outlook. What have I forgotten?

I've got web.config set to:
<add key="ISVIntegration" value="All"/>

isv.config.xml excerpt:
- <ToolBar ValidForCreate="0" ValidForUpdate="1">
<Button Title="Acumen" ToolTip="Acumen Enquiries"
Icon="/customicons/ico_statement16x16.gif"
Url="http://tnl-chc-crm1:5556/default.aspx" WinMode="0"
WinParams="dialogHeight:600px;dialogWidth:800px;" />
- <!-- A vertical toolbar spacer
-->
</ToolBar>