Manifest file to create a button on the ribbon in Outlook

I am very new to any form of coding, and I am trying to generate a manifest file so that I can deploy a button to our organization to add a button to their ribbon in Outlook.

The function is simple, I just want to button to take them to a webpage. I have included the manifest file I am using below.

<?xml version="1.0" encoding="utf-8"?>
<OfficeApp xmlns=
  "http://schemas.microsoft.com/office/appforoffice/1.1"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:type="MailApp">

  <Id>971E76EF-D73E-567F-ADAE-5A76B39052CF</Id>
  <Version>1.0</Version>
  <ProviderName>ECSC</ProviderName>
  <DefaultLocale>en-us</DefaultLocale>
  <DisplayName DefaultValue="Create Ticket"/>
  <Description DefaultValue="Open Freshservice to create a support ticket."/>
  <IconUrl DefaultValue="TESTURL.png"/>

  <Hosts>
    <Host Name="Mailbox" />
  </Hosts>

  <Requirements>
    <Sets DefaultMinVersion="1.1">
      <Set Name="Mailbox" />
    </Sets>
  </Requirements>

  <FormSettings>
    <Form xsi:type="ItemRead">
      <DesktopSettings>
        <SourceLocation DefaultValue="TESTURL"/>
        <RequestedHeight>216</RequestedHeight>
      </DesktopSettings>
      <TabletSettings>
        <SourceLocation DefaultValue="TESTURL"/>
        <RequestedHeight>216</RequestedHeight>
      </TabletSettings>
    </Form>
    <Form xsi:type="ItemEdit">
      <DesktopSettings>
        <SourceLocation DefaultValue="TESTURL"/>
      </DesktopSettings>
      <TabletSettings>
        <SourceLocation DefaultValue="TESTURL"/>
      </TabletSettings>
    </Form>
  </FormSettings>

  <ExtensionPoint xsi:type="MessageReadCommandSurface">
    <OfficeTab id="TabDefault">
      <Group id="msgReadGroup">
        <Label resid="groupLabel"/>
        <Control xsi:type="Button" id="msgReadOpenPaneButton">
          <Label resid="paneReadButtonLabel"/>
          <Supertip>
            <Title resid="paneReadButtonLabel"/>
            <Description resid="paneReadButtonDesc"/>
          </Supertip>
          <Icon>
            <bt:Image size="16" resid="icon16"/>
            <bt:Image size="32" resid="icon32"/>
            <bt:Image size="80" resid="icon80"/>
          </Icon>
          <Action xsi:type="ShowTaskPane">
            <SourceLocation resid="taskPaneUrl"/>
            <Title resid="paneReadButtonLabel"/>
          </Action>
        </Control>
      </Group>
    </OfficeTab>
  </ExtensionPoint>

  <Resources>
    <bt:Images>
      <bt:Image id="icon16" DefaultValue="TESTURL.png"/>
      <bt:Image id="icon32" DefaultValue="TESTURL.png"/>
      <bt:Image id="icon80" DefaultValue="TESTURL.png"/>
    </bt:Images>
    <bt:Urls>
      <bt:Url id="taskPaneUrl" DefaultValue="TESTURL"/>
    </bt:Urls>
    <bt:ShortStrings>
      <bt:String id="groupLabel" DefaultValue="Support"/>
      <bt:String id="paneReadButtonLabel" DefaultValue="Create Ticket"/>
    </bt:ShortStrings>
    <bt:LongStrings>
      <bt:String id="paneReadButtonDesc" DefaultValue="Open Freshservice to create a support ticket."/>
    </bt:LongStrings>
  </Resources>

  <Permissions>ReadWriteItem</Permissions>

  <Rule xsi:type="RuleCollection" Mode="Or">
    <Rule xsi:type="ItemIs" ItemType="Message" FormType="Read" />
    <Rule xsi:type="ItemIs" ItemType="Message" FormType="Edit" />
    <Rule xsi:type="ItemIs" ItemType="Appointment" FormType="Read" />
    <Rule xsi:type="ItemIs" ItemType="Appointment" FormType="Edit" />
  </Rule>

</OfficeApp>

I used the manifest file above, but the Integrated Apps area in the 365 admin center kept rejecting it.