Integration with Outlook Customer Manager
Contacts management should be integrated with Outlook Customer Manager. And Invoicing events and tasks appear in OCM history.
Andy Freedom commented
Since Outlook Customer Manager is "dead", you may be looking for replacement. If so, eWay-CRM is a great successor. The good thing is that it is much more than that. Just have a look.
:-(( OCM will be killed by the end of June 2020 - :-((
Please integrate Microsoft Invoicing with Outlook Customer Manager (or create a Flow template). When an estimate or invoice is sent, ideally, a new deal will be recorded in Customer manager. This would be a great way to bring the apps together. Integration is key.