Hi,
Avast BreachGuard can monitor an unlimited number of email accounts.
If you have Avast BreachGuard (Multi-Device), you can simultaneously activate your subscription on up to 10 devices, regardless of platform. You can transfer your subscription freely between devices and platforms. However, to activate Avast BreachGuard, you must sign in to the application with an Avast Account containing a valid Avast BreachGuard subscription.