What is credential theft?

Imagine someone gets hold of your email password. Not just your inbox, though. That one password could unlock your ESP account, your DNS settings, your entire sending setup. That's credential theft, and in the email world, the blast radius is bigger than most people expect.

Credential theft is when attackers steal the information that proves who you are online: usernames, passwords, API keys, and session tokens. Once they have those, they can walk into your accounts as if they're you.

The most common method is phishing. A fake login page looks identical to a real one, you type in your credentials, and they're gone before you ever notice. Other routes include malware that logs your keystrokes as you type, man-in-the-middle attacks that intercept login traffic, and large-scale data breaches where stored credentials are exposed all at once.

API keys and session tokens are worth calling out separately. They're not passwords, but they grant the same access. A stolen API key for your ESP account can let an attacker send email from your domain without needing your password at all. A stolen session token can give someone full access to an already-logged-in account, bypassing authentication entirely.

The damage doesn't stop at the first account either. Most people reuse passwords across services (you probably know someone who does, even if it's not you). That means one stolen password from a data breach somewhere else can unlock accounts on completely unrelated platforms. It's called credential stuffing, and it's one of the most common ways email infrastructure gets taken over quietly.

For email senders, a compromised account can trigger spam complaints, blocklist entries, and domain reputation damage that takes months to recover from. The attacker sends, you take the hit.

If you suspect something's off, our SOS hotline is free. We don't pitch you, we just help.