FormSettings element
Specifies source location and control settings for your mail add-in in older Outlook clients that only support up to Mailbox requirement set 1.2.
Note
Because the <FormSettings> element is required for manifest validation, it must be defined in all mail add-ins, including those that support Mailbox requirement set 1.3 or later. <FormSettings> is ignored when your manifest contains a VersionOverrides element.
Add-in type: Mail
Syntax
<FormSettings>
<Form xsi:type="ItemRead">
...
</Form>
</FormSettings>