We use web2lead form to submit lead from our website, but it would be fail sometime due to browser tracking protection or other reason.
So we decide to add the lead via background process, not from foreground like using ajax 
Is there a dll or api or web service that our partner can use to add the lead to saleforce ?
We have provide some info at setup/Build/Develop/api.  But our partner said it does not help.
Please give us some advice, Thanks