If that's the case, looks like this is happening because the domains with these errors are either unreachable or don't have valid MX records. This actually seems to be expected behavior- Prospeo is returning an invalid domain name error, which in these cases as they are reachable from my checking, means they don't have valid MX records and it's happening at a rate that is expected. Here's some more info from Prospeo about this:: [https:://prospeo.io/api/email-finder#::~~::text=The%20domain%20name%20you%20submitted%20is%20not%20reachable%20or%20does%20not%20have%20valid%20MX%20records](https://prospeo.io/api/email-finder#::~~::text=The%20domain%20name%20you%20submitted%20is%20not%20reachable%20or%20does%20not%20have%20valid%20MX%20records-Let)