When Drift Email finds an email address within a response it creates a new contact associated with that email address. Since replies can include the original sender (you), the ignored domains setting allows you to ignore any contacts at your own company. Another common use case for marketing teams is to ignore email addresses from the most common free email providers such as gmail, yahoo, and hotmail.
Go to Settings --> Contact Settings
Add the domains you want to ignore to the list
Ignored domains will apply to all future replies processed, but will not retroactively update old data
Note that this is a wildcard setting; any domain that includes the text configured will be ignored. For example, this configuration for hotmail.com will ignore email address from hotmail.com, reply.hotmail.com, hello.hotmail.com, etc.