Replicating the 'Send Using Outlook' button in Chrome or Firefox

Hi All

Has anyone found a way to replicate the 'Send Using Outlook' button on the new email screen, for use in browsers other than IE?

I know that the standard button is only available on IE due to its reliance on ActiveX, and I understand that Sage have no plans to implement it another way for other browsers.

So far, using a custom JS file, we've managed to produce a client side .eml file from a custom button, which is populated with the To address, Subject and body text from the CRM email. 

That all works fine but the final challenge is to populate the PDF attachment onto the message, for emailing quotes and orders, which we're stuck on ATM. 

When the CRM email is created, the attachment is saved on the server using a temporary folder name so it's not easy to specify the correct path.

Does anyone have any clever javascript to produce a fully formed .eml file, complete with attachment(s), or managed to do it another way?

Using v2020 R1.1

Thanks in advance