Need Little Help To Verify My Email List

Hi Guys Hope you all are fine

i have 2 year old huge email list of my clients i want to verify this list so i can use it again but i could not find any reliable software or service. if any body have any experience then please share with me i will be really thankful
Any reliable Email verifier service free or paid

Thanks in advance

the only way to verify them is to send email then seperate those bounces