Additional Notes on IPv6 Support

Advanced Configuration of Axigen

IPv6 in SPF

Support for IPv6 ranges (ip6) has been added when parsing SPF records. SPF now queries AAAA records when remote address is IPv6, A records when remote address is IPv4 (i.e. SPF "a" queries AAAA records when the remote peer is IPv6, same for "mx", "ptr").

Note: IPv6 wrapped IPv4 address are not handled (i.e. they are treated as IPv6 addresses — that means A queries are not performed as stated in RFC 7208).

IPv6 in Greylisting

Support for IPv6 addresses when computing the Greylist triplet has been added.

IPv6 in service banners (used in POP3, IMAP services, and proxies)

Support for IPv6 when printing listener address as part of the service banner has been added.

IPv6 in the FTP service

Axigen now implements the EPRT and EPSV commands used by IPv6 clients. See RFC2428 FTP Extensions for IPv6 and NATs, the RFC that describes extensions for data stream control commands.

While RFC2428 allows cross-protocol connections (a user can open a control connection through IPv4 and request a data connection through IPv6, and viceversa) Axigen does not permit cross-protocol connections (Axigen does not allow the user to request a data connection on a protocol that differs from the one used in the control connection).

IPv6 in Milter

Axigen is now capable of connecting to a Milter filter over an IPv6 TCP connection.

IPv6 in the RPOP service

The RPOP service now allows connections to POP3 server(s) over IPv6.

The POP3 server can be configured by IP (e.g. 2a02:XXXX:YYYY:0:20c:29ff:fe13:406b), in squared brackets notation (e.g. [2a02:XXXX:YYYY:0:20c:29ff:fe13:406b]), or by using the server name. When the name is used, Axigen will use the DNR service to retrieve A (IPv4) records; if retrieving the A record fails, a AAAA query is performed.