Capture emails in exchange to customers for all users in and out

We have a Exchange 2016 environment for emails and a Internal inhouse written .NET CRM system .  Our CRM system stores various details regarding customers , links to contacts details , notes and financial info.     We now want to capture emails from all staff within business so that we can then store them against the customer

So basically if someone sends or receives a email from a Customer in our database  then that email is then saved to a folder so it can be view against the customer record in our CRM system.     This will not be for one customer it will be for 400+ customers and from any email in the business.

If we went out and purchased something like goldmine or similar this has a Outlook plugin that does this into the goldmine database but in my case we want it in our own DB

Anyone got any ideas how I can capture this mails , if it needs to be a outlook plugin or could I run something on the backend machine

We currently use mail enabled public folders but problem is if the user doesn't include the e address in the email then it doesn't end up in it , I want the system to do this automatically , anyone got any ideas how to approach this

Thanks brian