Mimecast Secure Messaging vs Secure Message

Mimecast Secure Messaging helps organizations protect sensitive information sent by email, including financial records and customer data. It sends protected messages through a secure web portal; Mimecast says the information stays in its cloud. Senders can set read receipts and expiry dates, and restrict printing or replies. Messages and attachments are scanned for viruses, checked against data leak prevention policies, and stored in an AES-encrypted archive. Recipients log in to retrieve messages, download attachments, and reply securely. Gateway policies can initiate the service, and administrator-defined criteria can trigger Office 365 encryption when TLS is unavailable. Senders and recipients need no additional software or hardware. The service supports Android, iOS, macOS, web, and Windows, and includes Outlook integration and administrative access controls. Pricing is on request. The Critical, Advanced, and Premium plans all include secure message and large-file delivery and email continuity; their listed security coverage varies by plan.

Secure Message is a self-hosted inbound email gateway that filters mail before it reaches an existing mail server. Its Community features include Postfix content filtering, spam scoring, DNSBL, SPF, DKIM and DMARC checks, quarantine, mail logs and administrator MFA. Professional adds a recipient web portal: recipients open protected messages with a one-time code, without an account or app. Its rules can encrypt, redirect or block sensitive outbound messages, and recipient checks can use SMTP callout, LDAP or directory lookups. Stored messages, attachments and quarantine use Fernet encryption with AES-128-CBC and HMAC-SHA256; the key remains on the customer host. Access controls include TOTP administrator MFA, role-based access and audit logging, with logs exportable to CSV. Enterprise adds AI Autopilot tuning, eDiscovery and archive search, DLP and disclaimers; Autopilot and the classifier are off by default. The gateway can sit in front of Microsoft 365 or an existing mail server without mailbox migration. The single-node appliance runs on Debian 13, with 2 vCPU and 4 GB RAM recommended as a starting point.