How do I use appendOnSendAsync? - outlook

Question

I am trying to use the appendOnSendAsync API call for the Outlook Javascript API. Here is the link for it in the documentation. I've fulfilled all of the requirements needed to use this API such as being in preview and adding the Extended Permissions node in the manifest. I am using this API call on an OnSend event and getting this error: "Extended Permission missing from API call".
Here is my manifest file:
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<OfficeApp xmlns="http://schemas.microsoft.com/office/appforoffice/1.1"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:bt="http://schemas.microsoft.com/office/officeappbasictypes/1.0"
xmlns:mailappor="http://schemas.microsoft.com/office/mailappversionoverrides/1.1"
xsi:type="MailApp">
<Id>a5afbf03-dcfc-435c-8a7b-02f37f162796</Id>
<Version>1.0.0.0</Version>
<ProviderName>Contoso</ProviderName>
<DefaultLocale>en-US</DefaultLocale>
<DisplayName DefaultValue="No-Framework"/>
<Description DefaultValue="A template to get started."/>
<IconUrl DefaultValue="https://localhost:3000/assets/icon-32.png"/>
<HighResolutionIconUrl DefaultValue="https://localhost:3000/assets/icon-80.png"/>
<SupportUrl DefaultValue="https://www.contoso.com/help"/>
<AppDomains>
<AppDomain>contoso.com</AppDomain>
</AppDomains>
<Hosts>
<Host Name="Mailbox"/>
</Hosts>
<Requirements>
<Sets>
<Set Name="Mailbox" MinVersion="1.8"/>
</Sets>
</Requirements>
<FormSettings>
<Form xsi:type="ItemRead">
<DesktopSettings>
<SourceLocation DefaultValue="https://localhost:3000/commands.html"/>
<RequestedHeight>250</RequestedHeight>
</DesktopSettings>
</Form>
</FormSettings>
<Permissions>ReadWriteItem</Permissions>
<Rule xsi:type="RuleCollection" Mode="Or">
<Rule xsi:type="ItemIs" ItemType="Message" FormType="Read"/>
</Rule>
<DisableEntityHighlighting>true</DisableEntityHighlighting>
<VersionOverrides xmlns="http://schemas.microsoft.com/office/mailappversionoverrides"
xsi:type="VersionOverridesV1_0">
<VersionOverrides xmlns="http://schemas.microsoft.com/office/mailappversionoverrides/1.1"
xsi:type="VersionOverridesV1_1">
<Hosts>
<Host xsi:type="MailHost">
<DesktopFormFactor>
<SupportsSharedFolders>true</SupportsSharedFolders>
<FunctionFile resid="Commands.Url"/>
<ExtensionPoint xsi:type="Events">
<Event Type="ItemSend" FunctionExecution="synchronous" FunctionName="action" />
</ExtensionPoint>
</DesktopFormFactor>
</Host>
</Hosts>
<Resources>
<bt:Urls>
<bt:Url id="Commands.Url" DefaultValue="https://localhost:3000/commands.html"/>
</bt:Urls>
<bt:ShortStrings>
<bt:String id="GroupLabel" DefaultValue="Contoso Add-in"/>
<bt:String id="TaskpaneButton.Label" DefaultValue="Show Taskpane"/>
<bt:String id="ActionButton.Label" DefaultValue="Perform an action"/>
</bt:ShortStrings>
<bt:LongStrings>
<bt:String id="TaskpaneButton.Tooltip" DefaultValue="Opens a pane displaying all available properties."/>
<bt:String id="ActionButton.Tooltip" DefaultValue="Perform an action when clicked."/>
<bt:String id="AppendOnSend" DefaultValue="AppendOnSend"/>
</bt:LongStrings>
</Resources>
<ExtendedPermissions>
<ExtendedPermission>AppendOnSend</ExtendedPermission>
</ExtendedPermissions>
</VersionOverrides>
My Outlook version is: Version 2006 (Build 12914.20000) Office Insider