I have switched my job and now I am working in an multinational company. But, prior to that I was in a startup. There was a government project, which I almost did it by myself. I had a full day of knowledge transfer about the project before my last working day, and I had kept all necessary personnel in an email loop.
Now, the client for that project has approached me to ask for some information about the source code, the hosting server details, the website link, the progress made and so on. When I informed that I have left that company, the client said that he would ask me should he have more questions. I told him that I am no longer authorized to do anything related to that project. And I no longer have access to any information regarding the project, including any source code. I also told them to contact the respective people associated with the project.
But the client kept insisting that the people associated and the server management team, etc. are not helping them and that I would help them.
I have already informed some colleagues of my past company (whom I am in touch with), to inform the HR about this, but should I inform the HR of my current company as well? What should be my actions now?
Update:- I sent the client an email as follows, following @gnasher729's advice.
The officials from the <client> approached me in regards to the details of the <project>.Please note that I, <my name>, am no longer working on that project, and am no longer employed with my previous employer. In addition, I have transferred all the details of the project, including the source code, to the concerned people, as per the agreement with my former employer. I do not own/have knowledge on anything related to the project. So, the <project> is now the responsibility of <old employer>. Therefore, I request you <client> to contact <old employer> with queries related to the project (source code, the progress made, the login credentials and so on). Thanks and Regards <name>
Now, I got another call from client again, 2-3 days after sending this email, and he was asking me about the login credentials again. So, I informed my previous employer again. Then, I got a call from one of the employees from previous company, who is like an assistant to the old manager, who was asking me, if I remember the login credentials, the database table, the structure, etc. I told him that I don't remember, but he (the employee who asked me the database table and all) told me that he would ask me again, should he have more doubts. I seriously don't know what is going on, and I don't know how to answer that. I have done everything that was advised here, but I wasn't expecting my old employer to ask me details about the project, even when I had completed knowledge transfer , with 3-4 people.