During our search on the internet we found a provider that provides various e-mail addresses for free. Take a look at the massive e-mail list collection.
These lists can be used to send various e-mail campaigns.
The lists that can be downloaded for free are filled with public e-mail accounts which probably have been collected through malicious activities.
The lists are ordered on a alphabetic order so they can be easily be used for campaigns.
As you might imagine, cybercriminals will be using lists like these, but they will find more recent and active e-mail accounts on the darknet as there are massive markets which sell personal information and credentials.