I approached a client and for vitrifaction he wants mail ID of my all old client so i just want to have assistance of you guys that is it safe to give my clients mail ID to an unknown person?
If you are selling your business yes it is safe and ok, if you are not selling your business never share your clients email.
You are not allowed by law to share those details with anyone UNLESS you are selling your whole business OR the users agreed that you are allowed to sell/share their details with third parties.
no no i am not selling your business ... i was just searching for new clients. Thanks for your advice
As others have said the law stipulates that you can't do this, however, for future help you should ask clients when you deal with them if they would consent to you delivering their information to third parties in the future. If they give consent to this - Which they are likely to as it's as simple as ticking a box and usually people tick everything, you can give over their email addresses as per your new clients request.
I don't think giving old clients email ID for verification is good business practice. You can show your work portfolio or client testimonials but sharing private contact info is not good at all.