| | Roxen Community: RFC 3974 SMTP Operational Experience in Mixed IPv4/v6 Environments (Informational) (Site not responding. Last check: 2007-11-03) |
 | | For a single MX record, there are multiple possible final states, including: (a) one or more A records for the IPv4 destination, (b) one or more AAAA records for the IPv6 destination, (c) a mixture of A and AAAA records. |
 | | When there is no destination address record found (i.e., the sender MTA is IPv4-only and there are no A records available), the case should be treated just like MX records without address records, and deliveries should fail. |
 | | NOTE: If one or more address records are found, an implementation may sort addresses based on the implementation's preference of A or AAAA records. |
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