ORDB no longer exists | ExchangeDefender [ Skip to content ](#main) [ ![ExchangeDefender](/assets/images/xd_logo_blue.png) ](/) Email Security ![Platform Overview](/assets/images/m-xd-pro.png)### ExchangeDefender PRO Enterprise-grade email security made simple for every business. 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I hope you are not offended by the technical information regarding a third party service that may not affect you. In the old, dark ages of Internet when ExchangeDefender grew out of the primordial stew, people used connection-based filtering to blindly reject content using nothing but faith in the independent listing service. One of the popular realtime blacklists (RBL) was ORDB and it was a database of mail servers that were open relays. These servers could be used by anyone, without authentication of any sort, to send SPAM content all over the Internet. In December of 2006, ORDB went offline. On the morning of March 25, 2008 relays.ordb.org came back online, blacklisting everything. How, why, when and so on are not important, the only relevant task here is to stop using this RBL. If you receive the following context error, the remote server is still using ORDB to detect SPAM and it is dropping all your inbound mail: > The e-mail system was unable to deliver the message, but did not report a specific reason. Check the address and try again. If it still fails, contact your system administrator. > > < outbound.exchangedefender.com #5.0.0 SMTP; 530 Recipient refused. Open relay found, refer to [http://www.ordb.org/lookup/?host=65.99.192.91](http://www.ordb.org/lookup/?host=65.99.192.91)>" If you use Exchange 2003 Service Pack 2 you can quickly remove ORDB from your RBL query list by opening up Exchange System Manager, navigating to Global Settings, right clicking on Message Delivery and selecting properties. On the Connection Filtering tab you will find the RBLs you currently query. If you are protected by ExchangeDefender, this list should be blank. If you use a mail server other than Exchange consult your vendor. I hope you have a wonderful day and thank you for letting us manage your SPAM so you don't have to deal with the above every day :) Thank you for your business. Vlad Mazek [ Previous post The New Soul of ExchangeDefender March 11, 2008 ](https://www-preview.exchangedefender.com/blog/2008/03/the-new-soul-of-exchangedefender) [ Next post Want to hear what we are up to? March 26, 2008 ](https://www-preview.exchangedefender.com/blog/2008/03/want-to-hear-what-we-are-up-to) Related Posts ------------- [ 1 May ](https://www-preview.exchangedefender.com/blog/2026/05/exchangedefender-new-ui-is-live)### [ExchangeDefender New UI is Live](https://www-preview.exchangedefender.com/blog/2026/05/exchangedefender-new-ui-is-live) [Read more: ExchangeDefender New UI is Live](https://www-preview.exchangedefender.com/blog/2026/05/exchangedefender-new-ui-is-live) [ ![](https://storage.services.exchangedefender.network/exchangedefender-blog/blog/2026/04/xd10.png) 2 Apr ](https://www-preview.exchangedefender.com/blog/2026/04/announcing-exchangedefender-10)### [Announcing ExchangeDefender 10](https://www-preview.exchangedefender.com/blog/2026/04/announcing-exchangedefender-10) [Read more: Announcing ExchangeDefender 10](https://www-preview.exchangedefender.com/blog/2026/04/announcing-exchangedefender-10) [ ![](https://storage.services.exchangedefender.network/exchangedefender-blog/blog/2025/12/christmas-1.jpg) 25 Dec ](https://www-preview.exchangedefender.com/blog/2025/12/merry-christmas)### [Merry Christmas](https://www-preview.exchangedefender.com/blog/2025/12/merry-christmas) [Read more: Merry Christmas](https://www-preview.exchangedefender.com/blog/2025/12/merry-christmas) Search the blog Search Recent Posts ------------ - [ExchangeDefender New UI is Live](https://www-preview.exchangedefender.com/blog/2026/05/exchangedefender-new-ui-is-live) - [Announcing ExchangeDefender 10](https://www-preview.exchangedefender.com/blog/2026/04/announcing-exchangedefender-10) - [Merry Christmas](https://www-preview.exchangedefender.com/blog/2025/12/merry-christmas) - [Why IoT Devices Are a Hidden Security Risk for Your Business](https://www-preview.exchangedefender.com/blog/2025/11/why-iot-devices-are-a-hidden-security-risk-for-your-business) - [Top 5 IT Problems Small Businesses Face in 2025 — and How to Fix Them](https://www-preview.exchangedefender.com/blog/2025/10/top-5-it-problems-small-businesses-face-in-2025-and-how-to-fix-them) Categories ---------- - [Archiving](https://www-preview.exchangedefender.com/blog?category=archiving) (21) - [Business Continuity](https://www-preview.exchangedefender.com/blog?category=business-continuity) (13) - [Compliance](https://www-preview.exchangedefender.com/blog?category=compliance) (8) - [ExchangeDefender](https://www-preview.exchangedefender.com/blog?category=exchangedefender) (349) - [General](https://www-preview.exchangedefender.com/blog?category=uncategorized) (590) - [Hosted Services](https://www-preview.exchangedefender.com/blog?category=hosted-services) (86) - [Industry News](https://www-preview.exchangedefender.com/blog?category=industrynews) (29) - [Marketing](https://www-preview.exchangedefender.com/blog?category=marketing) (18) - [Phishing](https://www-preview.exchangedefender.com/blog?category=phishing) (5) - [PRO TIPS](https://www-preview.exchangedefender.com/blog?category=pro-tips) (44) - [Product Features](https://www-preview.exchangedefender.com/blog?category=product-features) (54) - [Security](https://www-preview.exchangedefender.com/blog?category=security) (65) - [Shockey Monkey](https://www-preview.exchangedefender.com/blog?category=shockey-monkey) (22) - [Spamfilter](https://www-preview.exchangedefender.com/blog?category=spamfilter) (5) - [Support](https://www-preview.exchangedefender.com/blog?category=support) (45) - [Webinars](https://www-preview.exchangedefender.com/blog?category=webinars) (44) Solutions --------- - [Stop Spam & Malware](/email-security) - [Hands-Free Email Backup](/livearchive-backup) - [Instant Email Recovery](/inbox) - [Send Private Emails](/corporate-email-encryption) - [Train Against Email Threats](/spearphishing) - [Share Files Safely](/web-file-server) Company ------- - [About ExchangeDefender](/about-us) - [Compliance & Legal](/our-compliance) - [Become a Partner](/partners) - [Support Portal Login](https://support.exchangedefender.com/) - [Microsoft 365 Email Management](/managed-email-operations) - [AI Advisory Service](/management-ai) ![ExchangeDefender](/assets/images/dark-xd-logo.png)USA: +1 (407) 465-6800 United Kingdom: 0800 8620149 Australia: +61 0390010641 Fax: +1 (954) 839-8737 [ ](https://www.facebook.com/ExchangeDefender) [ ](https://www.twitter.com/XD_Defender) [ ](https://www.linkedin.com/company/exchangdefender) [ ](/blog) © 2026 Own Web Now Corp - All rights reserved </> with ❤️ in Orlando [SLA](/sla) [TOS](/tos) [PRIVACY](/privacy-end-users) [AUP](/aup) We're Here to Help 👋 -------------------- Tired of AI 🤖 and hold music? 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