Skip to end of metadata
Go to start of metadata

You can use with individual domains. However, there are a few points you need to keep in mind, so please read this article carefully.

Using your own domain with

Note the following requirements:

  • You still need a normal account with your e-mail address.
  • If you registered your own domain somewhere in such a way that it belongs to you, you can view the MX records in the DNS data of your domain on 
  • In addition, you need to store a security key in the DNS data so that we know that the domain belongs to you. We will explain the details in a moment.
  • Once this has been done, you can create other e-mail addresses as aliases for your account. You continue to log in using your usual e-mail address; however, this account now receives e-mails with the created e-mail addresses of your own domain and you can select the created aliases as the sender when sending e-mails.
  • All accounts have their own, individual security key. This makes it possible to associate external domains to several accounts, if desired, simply by adding their different security keys to the DNS configuration.
  • It is not possible to use our enforced TLS sending (‘’) with your own domains.
  • It is possible to use an address from an external domain as your main account.

Step 1: The security key

Log in to your Office and go to Settings in the settings area. The ‘Add external addresses’ option is available under ‘E-mail Aliases’. Enter the desired e-mail address.

Our system then checks the DNS data to see whether this domain already contains the security key. If everything is OK, the alias will be created and can be used instantly. You can then proceed to step 2 of these instructions.

If there is no DNS security key, for example, because this is the first time you are registering an e-mail address of a domain with us, the system presents you with a DNS entry. To set the DNS security key you have to create a subdomain and set the TXT record of this sub-domain. Once you have updated this entry, you can try to register your e-mail address again.

The figure below shows an example:

  1. First you have to create the sub-domain “”.
  2. Than set the TXT record “c9652...xxxx....115a7” for this sub-domain.

Note: Due to the DNS cache times, it may take several hours before a newly created security key is visible on our systems!

own domian and securitiy keys

Step 2: Set the correct MX records

When our system finds the security key in the DNS, you can register e-mail addresses as aliases under this domain. Once you have done this and no errors have occurred, you can change your domain’s MX records so that they appear on the mail relays. Set the following MX records in the DNS: IN MX 10 IN MX 10 IN MX 20

Replace ‘’ with your own domain.

Note: As soon as your MX records appear on our server, we will receive all of your domain’s e-mails. If the target mailboxes were not set as aliases on our end, our system will reject the e-mails with a failure notification (‘User unknown’)! For this reason, always create mailboxes first and then change the corresponding MX records!

Step 3: Howto set the SPF records

SPF records should be configured in the DNS zone of your web domain. All you need to do is create an “include” statement for the SPF entries of Add a TXT or SPF record for your domain with the following content:


As a result, your current configuration will inherit the SPF settings of That means the IP addresses of our outgoing mail systems (which are used for sending your e-mails) will be passed on automatically. If you use more than one server for sending e-mails, you should extend the statement above to include their IP networks as well.

Please note that we cannot offer any further support for individual SPF setups. Also note that we tend to frown upon the use of “-all” in SPF records, when used for ordinary web domains. our systems are set up to interpret all occurrences of “-all” as “?all” by default, in order to maintain a reliable e-mail transmission service throughout. For details on this particular issue, please consult this talk about SPF/DKIM by the Heinlein Support GmbH.

Optional: How to enable auto-configuration in e-mail clients

If you would like to use the auto-configuration assistants offered by e-mail clients like Thunderbird or KMail, then you can do so by referring to an autoconfig XML file that is available on our web server. The easiest way to get this done is to add a reference in two particular DNS records for your domain name. These are the CNAME and the SRV records.

Set the following CNAME record to enable automatic e-mail configuration:

autoconfig IN CNAME

Set the following SRV record to enable automatic e-mail configuration:

_autodiscover._tcp IN SRV 0 0 443

Alternatively, you can upload an XML file that contains the required autoconfig data to your own web server. Please note the required location and naming conventions:

We have a template for this XML file, which you can simply download and edit before putting it onto your own server. Download the autoconfig file here. All you need to do is insert the corresponding entries for <domain>, <displayName> and <displayShortName>. Please see the example below:

<clientConfig version="1.1">
  <emailProvider id="">
    <displayName> mail server (Description)</displayName>
    <displayShortName>YDCOM (abbreviated name)</displayShortName>
    <incomingServer type="imap">

Further Questions – Help and FAQ

I do not have a domain. Can I register one on

No. is intended for anonymous use. Since we would need your address data for a domain registration, this would be in conflict with our “anonymous use” policy. In addition, works as a prepaid system, and if we were to register domains, the risk would be too great that complications would arise and we would have to delete them at some stage.

Can I take advantage of this offer with domains from other providers?

No. Changing the DNS MX records means that all e-mail traffic runs exclusively through It is not possible to redirect individual e-mail addresses to us. However, you could still use the option to have e-mail addresses from other providers as senders.

I don’t know what the DNS is. What should I change and where and how?

This option requires a certain amount of technical expertise regarding how domains work which includes knowing what DNS is. If you have purchased your own domain, you will probably have done that through a specific provider (registrar). Contact your registrar for help with setting up your DNS for

Can help me solve problems with DNS setup for my own domain?

No. Contact the provider that you purchased your domain at.

Can I use DKIM?

In order to enable DKIM for your embedded domain, we need to generate a domain-specific DKIM key and distribute this key on our systems. If you wish to enable DKIM, please raise a support ticket at and let us know the domain name with which you would like to use DKIM.

As soon as the necessary steps have been implemented, you will receive a pair of keys from us. First, a private key, which you should keep secure. Further, a public key, which needs to be published in your DNS zone. Please be aware that we cannot provide any additional support for DKIM beyond this.

What can I do if I no longer want to run my own domain on

You can switch at any time. Change your domain’s MX records to the desired new provider and don’t forget to delete the created aliases from your account.

Can I use catch-all addresses with my own domain with

Yes, that's possible. Have a look at our own domain at for using own domains.

Is there a limit to the number of e-mail addresses?

Yes. As far as is concerned, the aliases created under your own domain are normal aliases. The possible number varies depending on the package. Please refer to our table of packages. If you create additional aliases, it may be necessary to switch to a better mail package when your permitted aliases are no longer sufficient.

Can I remain anonymous while using my own domain name?

Yes. While in principle, a domain name will always allow others to retrieve related ownership information using a registrar website or other whois-database, there is a way to remain anonymous by hiding this information behind a „whois-proxy server“.

Many ordinary domain providers in Germany are offering this kind of service to customers. For instance, the company „CPS Datensysteme“ has proxies covering more than 200 different top-level domains:

Internationally, there are a number of reliable (!) providers that allow anonymous domain registration:

Can I use this for my organisation/business?

Yes and No. has been designed for use by freelancers or small businesses. If there are several people who want to use email accounts with the same domain name, each of them will need their own account. For each of these accounts a security key needs to be added to your DNS entries. Unfortunately shared calendars and address books can not yet be used in such configurations.