Adding users to mailing lists

Our website has been POSTing to https://XXX.infusionsoft.com/app/form/process/xxxx to add new users to our mailing lists. We are now getting a HTTP Code 308 Permanent Redirect error.

What is the new URL we should use?

I think I heard that this is no longer a supported option. @Mark_Penney - can you verify?

Do you have Zapier or something like it you can use?