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Open Source Email Security Software (2026)

Last updated: March 2026

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4 software options

Proton Mail logo

Web-based email management platform

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servermx logo

Email Hosting Solution

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mxHERO Email Attachment Protection logo

Email Security to protect data sent by email attachments

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Open Source
Discount pricing available above 25 users. 30-day cancellation.

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Stalwart logo

Open-source mail and collaboration platform

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Open Source
Stalwart uses tiered, per-mailbox pricing that scales with your organization’s size. Larger mailbox volumes receive progressively lower rates, and bulk discounts are available for high-volume deployments.

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