What is Mimecast?
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If you've received a company email that shows "Rewritten by Mimecast Security" in the footer, you've already encountered it in the wild.
Mimecast is a cloud email security platform aimed primarily at enterprises and larger organizations. It sits between your mail server and the outside world, screening everything that comes in and sometimes everything that goes out. The platform bundles several capabilities that companies often need separately:
Threat protection: URL rewriting (Mimecast rewrites every link in an incoming email to route through their scanners, so if you click a link that turns out to be malicious, they can block it even after delivery), attachment sandboxing (suspicious files get detonated in an isolated environment before you see them), and impersonation detection (catching emails that look like they're from your CEO but aren't).
Email continuity: If your email server goes down, Mimecast provides a backup inbox so you don't lose access. Useful for organizations where email downtime is genuinely costly.
Archiving: Long-term email retention with search, for legal and compliance purposes.
Where it competes: Proofpoint is the most common alternative in the enterprise space. Both position themselves as full security suites rather than point solutions.
If you're evaluating Mimecast for your organization, the most relevant questions are about your specific threat model and whether you actually need the continuity and archiving modules or just the threat protection. For smaller operations, the pricing and complexity may be more than the risk warrants. Our SOS hotline is free if you want a second opinion on whether a platform like this fits your setup.
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