gpg4o
gpg4o: A focused Outlook add-in for Windows users who need OpenPGP encryption and signing. Ranked #17 of 29 in Email Encryption Software by our editors (7.5/10); pricing: Free plan · 180-day trial; best for windows Outlook users needing OpenPGP.
At a glance
- Editor score7.5 / 10
- PricingFree plan · 180-day trial
- Best forWindows Outlook users needing OpenPGP
- Free planYes
- Secure deliveryAttachment
- Facts checked20 Sep 2026
Where it wins
- Encrypts, decrypts, signs, and verifies messages and attachments
- Supports public and private keys, key servers, and synchronization
- Adds Enterprise KeyServer and Microsoft Policy Manager controls
Where it doesn't
- Windows-only platform coverage
- Paid licensing starts at €99.95 per license
- Free version has limited functionality
Our verdict on gpg4o
gpg4o is a Microsoft Outlook add-in for Windows users who need OpenPGP email encryption within a familiar workflow. It encrypts and decrypts email messages and attachments, signs and verifies them, and supports asymmetric encryption through OpenPGP and GnuPG. The product suits individuals and business teams that need public and private key management without moving away from classic Outlook. Supported Outlook versions include Microsoft Outlook 2016, 2019, 2021, and 365 Classic.
The pricing structure combines a free option with paid licensing. gpg4o Free has no time limit, but its functionality is limited. The paid gpg4o plan costs €99.95 per license as a one-time purchase and includes all functions of the OpenPGP encryption system. A 180-day free trial is also described for the product. Optional maintenance costs €51.95 per license for one year or €139.95 per license for three years, covering updates and support. This makes the paid plan more suitable for users who need the full feature set and ongoing maintenance, while the free version is better for evaluating a narrower feature set.
Its strongest fit is the Microsoft Outlook and OpenPGP ecosystem. gpg4o supports local and public key servers, automatic key synchronization, and central key management through Enterprise KeyServer. Microsoft Policy Manager and automatic key generation add administrative controls for business deployments. The trade-off is a narrow platform focus: gpg4o is Windows-only, integrates with Microsoft Outlook rather than Gmail, and is not open source. Choose it for Outlook-centered OpenPGP workflows and centralized key controls; consider an alternative if you need broader platform coverage or Gmail integration.
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gpg4o pricing
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gpg4o fact sheet
| Free plan | Yes |
|---|---|
| Paid from | Not verified |
| Secure delivery | Attachment |
| Recipient verification | Identity |
| Message expiry | No |
| Attachment limit | Not verified |
| Outlook integration | Yes |
| Gmail integration | No |
| Admin access controls | Yes |
| Free trial | 180 days |
| Deployment | Desktop |
| Platforms | Windows |
| Support | Email, Docs |
| Built for | Small business, Mid-market, Enterprise (editorial estimate) |
| Integrations | 3 integrations: Microsoft Outlook, GnuPG, Enterprise KeyServer |
| Pricing | Free plan · 180-day trial (source) |
| Website | bayoosoft.com |
| Facts checked | 20 Sep 2026 |
gpg4o integrations
gpg4o lists 3 integrations on its own site.
- Microsoft Outlook
- GnuPG
- Enterprise KeyServer
Alternatives to gpg4o
- FlowCryptA broad OpenPGP option for Gmail and mobile users, with enterprise controls for managed deployments.9.4
- c.EmailA free, open-source option for encrypted Gmail and Outlook email.9.2
- MailvelopeA browser-based OpenPGP option with broad webmail support and organization controls.9.0
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Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026
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