Just saw a package called obuchmann/odoo-jsonrpc search for it on packagist, I will test it this week!

Thanks for help, i test ...

Check the Odoo external API docs, the API is quite good in my opinion, i use it to enrich leads with tracking data. If you want to build these kind of custom modules id suggest you try hosting Odoo yourself. You can build custom modules and test them pretty easily in a development enviroment. 

What i would do is create a custom python module in Odoo. 

1. Look if you could get an API to your mailserver, retrieve the mails with a model in your custom python module. 
2. Setup a scheduled action in Odoo that calls the python model to retrieve the mails every hour or so.
   
3. Then, parse the mail data and convert it into a list of python dictionaries. (1 per email, with sender data etc.) 
4. Iterate trough the list and send each dictionary using xmlrpc to the Odoo external API to create leads.
5. Done!

Hope this was of any help.

Cheers! and Happy Coding!