Web and Mail Servers with IPv6
ACLs, Graylisting, Proxies
ACLs that define which IP networks accept mails without authentication (relaying) or that refuse mail are common pitfalls. Add your own IPv6 network to the relaying settings first, to make sure messages that reach the system via IPv6 get through. If you implemented graylisting with a MySQL back end in your mail configuration, make sure the fields are long enough for the IPv6 addresses.
Again, test everything related to IPv6. To do so, set up the IPv6 address, or the IPv6 test host name temporarily as your mail server in your mail client. If this doesn’t work, check the mail server configuration and the client.
Many proxy daemons such as anti-virus or PGP encryption are not IPv6 compatible. You might want to disable the proxy services while you experiment. A permanent solution is a static IPv4 address on the mail client, or you could create a particular hostname such as ipv4.mail.Domainname.com with the suitable IPv4 addresses only.
Joining Forces
After completing these tests, the plan is to enable the host and domain names for parallel IPv4 and IPv6 support.
To do so, add suitable AAAA records to the corresponding DNS settings for IPv6 in your DNS. Choose a very low TTL for the DNS record, if possible. Doing so will help you quickly disable the IPv6 address without the DNS cache keeping the last status for too long.
After adding IPv6 records to your DNS settings, you can try out the new names. Before you do, however, restart the Apache service, especially if you use DNS-based virtual hosts. If everything works, change the DNS reverse records to the correct names and remove the test domain ipv6.Domainname.com .
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