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SPECIFICTION
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gpg4o

bayoosoft.com

From €99.95/mo Free plan Windows
Visit bayoosoft.com
Spec score 8.7 #5 of 31 in Email Encryption Software

What it is

gpg4o is a Microsoft Outlook add-in for encrypting, decrypting, signing, and checking messages and attachments. It uses public and private keys under the OpenPGP standard, and supports encrypted HTML email, PGP/MIME, and PGP/Inline. Its key management can synchronize keys, use local or public key servers, and check the Web of Trust; central management requires Enterprise KeyServer. The product also supports terminal servers, Microsoft Policy Manager, automatic key generation, and working groups. When encryption is enabled, it protects message text and attachments, but not the subject line or recipient list. The current feature page lists Outlook 2024 or 365 Classic on Windows 11 and marks Mac OS unsupported. A limited free version is available without a time limit, and a 180-day trial is noted. The listed gpg4o plan costs €99.95 a month. After maintenance expires, users can still send and read encrypted or signed email, but they do not receive further updates.

Spec sheet

Product
gpg4o is a Microsoft Outlook add-in for encrypting, decrypting, signing and checking messages and attachments.Read 28 Sep 2026 · bayoosoft.com
Free plan
YesRead 20 Sep 2026 · bayoosoft.com
Support
Technical support is available through the contact process or the gpg4o Help menu in Outlook, with a log file sent automatically.Read 28 Sep 2026 · bayoosoft.com
Headquarters
Darmstadt, GermanyRead 28 Sep 2026 · bayoosoft.com
Admin access controls
YesRead 20 Sep 2026 · bayoosoft.com
Compatibility
The maker lists compatibility with Symantec Encryption, Enigmail, KMail, Apple Mail, K9-Mail and iPGMail.Read 28 Sep 2026 · bayoosoft.com
Encryption
It uses asymmetric encryption with private and public keys and follows the OpenPGP standard.Read 28 Sep 2026 · bayoosoft.com
Encryption boundary
When encryption is enabled, the message text and attachments are protected but the subject line and recipient list remain unencrypted.Read 28 Sep 2026 · bayoosoft.com
Enterprise features
gpg4o supports terminal servers, Microsoft Policy Manager, automatic key generation and working groups.Read 28 Sep 2026 · bayoosoft.com
Gmail integration
NoRead 20 Sep 2026 · bayoosoft.com
Key management
Key Server Management supports automatic synchronization, local and public key servers, and Web of Trust checking; central management requires Enterprise KeyServer.Read 28 Sep 2026 · bayoosoft.com
License use
A license can be used on several computers and profiles when the licensed email address is configured in Outlook on each computer.Read 28 Sep 2026 · bayoosoft.com
Log privacy
The maker says gpg4o log files contain no personal information, passwords or email contents.Read 28 Sep 2026 · bayoosoft.com
Mail formats
It supports encrypted HTML email, PGP/MIME and PGP/Inline.Read 28 Sep 2026 · bayoosoft.com
Maintenance expiry
After maintenance expires, users can continue sending and reading encrypted or signed email but receive no further updates.Read 28 Sep 2026 · bayoosoft.com
Message expiry
NoRead 20 Sep 2026 · bayoosoft.com
Outlook integration
The add-in provides end-to-end encryption directly through the Outlook interface.Read 28 Sep 2026 · bayoosoft.com
Recipient verification
identityRead 20 Sep 2026 · bayoosoft.com
Secure delivery
attachmentRead 20 Sep 2026 · bayoosoft.com
Supported desktop
The current feature page lists Microsoft Outlook 2024 or 365 Classic on Windows 11 and marks Mac OS unsupported.Read 28 Sep 2026 · bayoosoft.com
Target users
The product page positions gpg4o for professional confidential communication and private sharing of sensitive information.Read 28 Sep 2026 · bayoosoft.com
Trust credentials
BAYOOSOFT lists Security Made in Germany by Teletrust, ISO 9001 quality management and a TISAX assessment.Read 28 Sep 2026 · bayoosoft.com

Plans and prices

gpg4o €99.95 a month All functions of the OpenPGP encryption system · Microsoft Outlook 2016/2019/2021/365 Classic Read 20 Sep 2026 · bayoosoft.com
gpg4o Free Free Free version without a time limit · Functionality is limited Read 20 Sep 2026 · download.giepa.de
gpg4o – Extension product maintenance 1 year €5,195 a year one year Updates and support for gpg4o Read 28 Sep 2026 · bayoosoft.com
gpg4o – Extension product maintenance 3 years €13,995 a year three years Updates and support for gpg4o Read 28 Sep 2026 · bayoosoft.com
gpg4o €9,995, paid once one-time license Microsoft Outlook 2016/2019/2021/365 Classic · OpenPGP functions Read 28 Sep 2026 · bayoosoft.com

Every gpg4o plan and price →

Strong points and limits

Strong points

  • Supports encrypted HTML, PGP/MIME, and PGP/Inline.
  • Key management supports local and public key servers.
  • Offers a limited free version without a time limit.
  • Supports terminal servers and working groups.

Limits

  • Subject lines and recipient lists remain unencrypted.
  • Mac OS is marked unsupported.
  • Central key management requires Enterprise KeyServer.
  • Paid plan is €99.95 a month.

Who it suits

gpg4o suits Outlook users who need OpenPGP encryption, signing, and key management for confidential email. Its listed current support is for Outlook 2024 or 365 Classic on Windows 11.

Verdict

gpg4o provides OpenPGP tools within Outlook, including multiple mail formats and key-management options. Readers should note the Windows support scope and that encryption does not cover subjects or recipient lists.

Where Specifiction places it

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