Email list hygiene / scrubbing suggestions?

Hi all -- new here to the Warrior Forum -- it looks like there's a wealth of information here from a lot of established folks in the industry...great to see.

Here's my question -- my company maintains some websites that collect permission-based optins, which we then API feed into our ESP (GetResponse).

We'd like to try to minimize the amount of phony email addresses that are being submitted through our web forms (and ultimately reduce our bounce rate) -- but prefer not to have to go the route of obtaining double-optins if we don't have to.

So does anyone know of a company or service that provides list hygiene or "pre-scrubbing" so to speak -- some kind of intermediary that we could pass our data off to immediately after the web form submission for scrubbing who would then pass back to us with a "thumbs up" on the email address?

I asked my IT guys about this and they said that in the past, you could just "ping" the ISP to verify whether the email address is legitimate or not, but this has since been done away with to prevent people from hammering mail servers looking for valid addresses, which makes sense.

Any suggestions from you veteran emailers out there?

Thanks!