What is Secure/Multipurpose Internet Mail Extensions (S/MIME)?

Secure/Multipurpose Internet Mail Extensions (S/MIME) is an email security standard that uses digital certificates, encryption, and digital signatures to protect email communication. It helps verify the sender, detect message tampering, and prevent unauthorized users from reading sensitive email content.

Multipurpose Internet Mail Extensions originally expanded email so messages could carry rich content such as attachments and non-ASCII text. S/MIME adds a security layer to that email format, making it useful for enterprises that exchange confidential documents, approvals, contracts, financial data, healthcare records, or customer information.

How does S/MIME work?

S/MIME relies on public key infrastructure, or PKI. Each user receives a digital certificate that contains a public key and is issued by a trusted certificate authority. The public key can be used to encrypt messages sent to that user, while the user’s private key decrypts the message.

S/MIME also supports digital signing. When a sender signs an email, the recipient can confirm that the message came from the claimed sender and was not altered in transit. This is especially important for business workflows where email authenticity affects legal, financial, or operational decisions.

What does S/MIME protect?

Why is S/MIME important for enterprises?

For IT and security teams, S/MIME reduces the risk of data exposure through intercepted emails, impersonation, and message manipulation. It is commonly used in regulated industries, executive communication, legal correspondence, and environments where email must support confidentiality and non-repudiation.

However, S/MIME is only effective when certificates are properly issued, deployed, renewed, and revoked. Poor certificate lifecycle management can lead to failed encryption, user friction, and gaps in email protection.

How Hexnode supports S/MIME security

Hexnode helps IT teams deploy and manage email security configurations across managed endpoints from a centralized UEM console. Organizations can enforce device-level policies, configure work email settings, distribute certificates, and reduce manual setup errors across mobile and desktop devices.

For businesses using Multipurpose Internet Mail Extensions with S/MIME, Hexnode strengthens operational control by ensuring that only compliant, managed devices access corporate email. This helps align secure email communication with broader endpoint security, identity, and compliance requirements.

When should businesses use S/MIME?

Businesses should use S/MIME when email contains sensitive information or when sender authenticity matters. It is especially valuable for organizations that need encrypted business communication, certificate-backed trust, and stronger assurance that emails have not been modified.