If you are about to reach out to a large list, it's good to initially run email validation. It will return back valid/invalid email addresses.
Though, the email validation systems are also not a 100% correct as they don't actually send the email - they just test of the recipient server is willing to accept the email.
Valid → Good to go (still may bounce, but unlikely)
Accept All (Unverifiable) → May go through but not likely that the email address is being actively monitored, okay to experiment with
Unknown → Only experiment with if you have a low overall bounce-rate
Disposable → Discard
Invalid → Discard
Our recommendation is to experiment with some of the unsure emails to see what results they generate.
Bounces
Bounces can temporarily have a negative impact if the email with the same content bounces for multiple people who all have their emails in the same server. In that case your emails might get throttled by the recipient server. The server and domains that we use to deliver the email also get hit if there are many bounces and it might land us in some blacklists.
In general a bounce rate under 2% is ok and shouldn't raise any alarms.
Outfunnel actively also monitors this on their end and bounces are only one of the many signals that they use.