A third-party email provider is an external service that sends, receives, or manages email for an organization. This can include mail delivery, sender reputation, inbox infrastructure, contact lists, or automated notifications. Many companies use these services because they are reliable, scalable, and easier to manage than running their own mail systems.
In cyber security, this matters because email is a trusted communication channel. If an attacker compromises the provider, they may abuse a brand’s legitimate sending infrastructure to deliver convincing phishing messages, reset-request emails, or fraudulent support notices. That can turn ordinary customer outreach into a high-trust attack path, even if the organization’s core systems are untouched. Defenders reduce this risk with strong provider security, account hardening, phishing-resistant authentication, monitoring for unusual mail activity, and clear user guidance that says legitimate support will never request secrets such as recovery seeds or passwords.