Best way to check hundreds of emails fast before a campaign?

We're trying to do B2B email outreach but properly and the first issue I see is and email verification. I know there are lots of "tools" that can help, but I already have a list of a few hundred leads that we KNOW are good to target.

Problem is much simpler - I don’t want to risk high bounce rates and tanking my sender reputation. I know in theory you can use bulk email verification tools that check if an address is valid and some of them work directly with your CRM. Snov io has been recommended a lot for this.

But the things I already tried take time and cost way too much for what's meant to be a "small campaign". And even if I got something that's paid (one time, by volume, monthly, whatever) - I have to know it's GOOD.

If you know anything that does this fast and does it well, please recommend something.