Tools to crack email accounts

Hi,
So basically I once had a really helpful tool that allowed me to brute force email accounts and then check them for emails received from [email protected] for example. But I stopped cracking accounts because my router couldn't handle it so I quit and just removed my tools (system reinstall actually). Anyway, summer now so let's do this again but I am out of tools now so does anyone knows what's the name of this tools? Thanks!