Are emails verifier programs give real results ?

Are emails verifier programs give real results ?
I personally doubt it !!
I had 8 active emails put in txt file and tested them within 4 programs to make sure they r valid
and each program gives different results ????!!! some gives : 3 valid and 5 invalid .. although all emails r active and I use them almost every day !
The programs used r : live email verifier professional - smart email verifier - atomic email verifier and valid email verifier
The question is : To what extent can we trust these programs ? what is wrong with them ?

No, they don't give real results in many cases.

I was looking for a legit solution as well. Heard a lot of mixed results and honestly they are software I have never tried before. That said, I'm looking for a somewhat decent way to clean an older opt in list that I'm sure needs a lot of scrubing at this point.

And I'd rather not blow thru a ton of IPs etc trying to clean out the bouncebacks.