If you are using an older Dynamics 365 online/on-premise, you might likely be missing seeing the Dynamics 365 App For Outlook because it wasn’t originally added to SiteMap and you might not have added.

Use Shortcut provided by Microsoft Support

1. Let’s say your Organization URL is https://<org&gt;.crm.dynamics.com/
   Then, append the below link to the Organization URL to make it look like this
   https://<org>.crm.dynamics.com/tools/appsforcrm/AppForOutlookAdminSettings.aspx
   
   And this will open up the Dynamics 365 App For Outlook
   
   
2. You can also add it permanently to your SiteMap by following this Microsoft Support article from which I picked the link for you –
   https://support.microsoft.com/en-in/help/4339287/dynamics-365-app-for-outlook-missing-from-dynamics-365-navigation
   
   One a side note, Dynamics 365 App For Outlook is also supported for D365 on-prem. Follow this Microsoft article to know more – https://cloudblogs.microsoft.com/dynamics365/no-audience/2016/12/13/dynamics-365-app-for-outlook-support-matrix?WT.mc_id=DX-MVP-5003911
   
   

Hope this helps!!