How does password reuse enable compromise?

Password reuse means one breach exposes multiple accounts. Attackers obtaining credentials from any breached service test them everywhere. Your email password used elsewhere becomes vulnerable to any breach.

Attack chain: service breach exposes credentials, attackers test against email providers, reused passwords grant access, email account compromise enables further attacks (password resets, **impersonation**).

Prevention: use unique passwords for every service, especially email. Password managers generate and store unique passwords. Email accounts deserve strongest protection since they enable recovery of other accounts.