Technical infrastructure update: is now accepting IPv6-based connections

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Executive summary:

The admin team has been working hard to improve our infrastructure, with the result that our server systems now accept connections via the latest version of the internet protocol IPv6. Customers who use devices that support IPv6 will benefit from connections that get established quicker and show improved latency. now offers all customers the option to use IPv6-based connections to our server systems. With our latest infrastructure update, e-mail services, website, and the cloud office can be accessed through this latest version of the internet protocol. With IPv6, customers benefit from lower latency times and better connection speed. The only requirement: Devices and internet connection at the client side need to be able to “speak” IPv6 as well. However, most broadband- or cable internet providers will support IPv6 already and those that don’t will likely do so soon. Needless to say, mobile devices like smartphones and tablet computers increasingly communicate via IPv6, too.

For example, if a compatible device connects to “” to retrieve e-mails, then that server will automatically resolve an IPv6 address without the need for any separate configuration. Devices that do not support the new protocol version can still use all services as usual with the IPv4 protocol, because provides interfaces for both the old and the new protocol in parallel (Dual Stack).

The new technology also helps increasing our reach towards other parts of the world. For instance, most of the broadband connections on offer in Asian countries have already dropped support for IPv4 and exclusively communicate through IPv6. If internet services don’t support the new protocol, they remain practically invisible to these users. services that can be accessed through IPv6:

  • Website:, user forum, helpdesk, knowledge-base
  • Cloud office:
  • E-mail (IMAP):
  • E-mail (SMTP):
  • CalDAV/CardDAV/WebDAV:
  • HKP-Server:
  • Download-Links:


In summary, all our systems that users communicate with directly support both IPv4 and IPv6. On the back-end side, the MX relay servers, which internet providers use to exchange e-mail traffic, still run on IPv4. We decided not to upgrade these just yet, as we expect there may be communication problems if we did this too soon. The reason is that not all providers (and especially the spam protection software they use) would currently cope equally well with the new protocol. There is also no real technical advantage in upgrading the MX relays to IPv6, so leaving things as they are for the time being will protect users against unwanted side effects.


About IPv6

The number of internet-connected devices is growing at an increasing scale, and it is foreseeable that the amount of internet addresses that can be provided under the IPv4 protocol will soon not suffice any more. IPv6 offers a vastly greater address space to solve this problem – about 340 sextillion addresses as opposed to IPv4’s 4.3 billion addresses.(*) In some Asian countries, IPv4 addresses are already getting scarce, leading to many providers requiring IPv6 for all internet connections. The “old” IPv4 protocol is still more widely used in Europe but its replacement with IPv6 is already in progress.

(*) Source: