Messaging Server, RBL, and dns_verify
(Doc ID 1932937.1)
Last updated on FEBRUARY 03, 2025
Applies to:
Oracle Communications Messaging Server - Version 5.0.0 and laterInformation in this document applies to any platform.
Purpose
This article will address questions around the use of Real-time Block Lists (RBLs) and Domain Name Service (DNS) Verification in the Messaging Server MTA.
RBL and DNS Verification are actually separate things. But RBL checking makes use of dns_verify. This article is more about how to use the dns_verify routines.
Questions and Answers
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In this Document
| Purpose |
| Questions and Answers |
| Do you really want to do this? |
| Realtime Block Lists (RBLs) |
| Normal DNS Usage by the MTA |
| Two things called DNS Verify |
| DNS Verify and RBL |
| Ok, How do I use this? |
| Options for configurating RBL |
| ENABLE_RBL or DNS_VERIFY_DOMAIN in dispatcher.cnf |
| The dns_verify library routines |
| A brief word about mappings tables |
| Use the dns_verify_domain_port routine in the PORT_ACCESS table |
| Use the dns_verify_domain routine in the MAIL_ACCESS or ORIG_MAIL_ACCESS tables |
| Syntax of dns_verify_domain and dns_verify_domain_port |
| Continuation Lines in Mappings Tables |
| Use the dns_verify (or dns_verify_ptr) routine in any table |
| The dns_verify_ptr argument syntax |
| Using dns_verify to do RBL lookups |
| When DNS fails - why you need return-if-indeterminate |
| Symbolic Substitution - Return Values |
| MTA Performance problems caused by RBL and DNS performance |
| Why is it so bad? |
| What else can we do about it? |
| Or have local users go thru a different service |
| Improvements in Messaging Server 6.3 |
| References |