It is possible to add a deeplink to the bpost eTracker by using your own customer reference. In case you use the bpost Shipping Manager, this is your order ID.
Please bear in mind that other customers may also use a similar order numbering. So, should you wish to use this solution, then we suggest to use an appropriate order numbering logic to ensure unique values e.g. "MyCompany_2015043001", rather than "123".