DNSBL Return Codes
DNSBLs may return DNS A or TXT records. The TXT record (if present) usually returns text that can be displayed to the user as part of the SMTP error text.
Multiple A records can be returned but must always be in the range 127.0.0.0/8, but must not be 127.0.0.1 (this is defined as the return code to say the DNSBL may have shut down and should not be queried) and 127.0.0.2, which is used as a test point and must be present.
The remainder of the 127.0.0.0/8 range can signify individual lists within an aggregated list or partition one big data set into multiple smaller pieces so that the user may treat each differently should they wish.
All return codes for Abusix Mail Intelligence lists are defined in our documentation.Back to Glossary