Using e-mails with a custom domain

mailbox customers (except those on the Light price plan) may use our servers to send e-mails from addresses that have another domain name (e.g., me@example.com). Similarly, it is possible to use e-mail addresses from an external domain as aliases for your mailbox account (the maximum number of aliases permitted will depend on your chosen price plan). Once your custom domain name has been set up properly with mailbox, you will also receive e-mails in your inbox with us that are addressed to the e-mail addresses of that domain. Of course, you can also use the external e-mail addresses as a sender identity and define one of them as your main address. The instructions below outline how this works, possible issues you should bear in mind, and how to set everything up.

Information for Business Account Customers

This guide is intended for our private customers. If you are using a Business Account, please follow the instructions provided in this article. this article.

Preparations

To use mail addresses with an alias of your own domain, you will need the following:

• A domain that you have registered with a provider of your choice. In this article, we will use the domain example.com as an example.
• The login credentials for the management interface of your domain, provided by your provider or hosting service. Common providers include Hetzner, Netcup, or INWX.

For administrators of a family account, there are two options for integrating the domain:

• All family members can use the external domain.
• Only the administrator of the family account can use the external domain.

Note on Data Processing and Storage

Mail from domains that are forwarded and sent via mailbox is processed and stored on our servers.

Step 1: Retrieve the mailbox Security Key

1. Open the Settings in the mailbox user interface.
2. Click on the menu item "Mail Addresses".
3. Select the submenu "Mail Aliases".
4. In the input field "Add external alias", enter the desired mail address using your own domain (e.g., bernd.mustermann@example.com).
5. Click "Save".

Figure 1: Add external Alias.

In the background, mailbox now checks whether the security key is already stored in the DNS records of your domain.
If you are adding the alias for the first time, you will see the message
"Error: Validation of the external domain failed", and new security keys will be generated for the domain.

Security Keys for Individual mailbox Accounts

If you are using your mailbox account as an individual (not a family account), the following will be displayed (Figure 2):

Figure 2: Validating an external Alias.

Security Keys for mailbox Family Accounts

If you have a family account, there are two options for using your domain:

• Fields (8) and (9) provide the data required to set up the domain for the entire family (see Figure 3).
• Fields (10) and (11) allow you to use the domain as the family administrator only (see Figure 3).

Figure 3: Some of the images in this article are currently being updated or added. We're working to provide the missing screenshots as soon as possible. Thank you for your patience and understanding!

Differences Depending on the Provider

Since each provider uses different web applications to manage domains and DNS records, the required formats may vary. mailbox therefore only provides general recommendations.

If you are unsure, please contact your provider’s support team and refer them to this guide. Typically, when you register your domain, you will receive login credentials that allow you to access the provider’s administration interface and make the necessary configurations.

Step 2: Add the mailbox key to your domain provider's DNS settings

The configuration may vary depending on the provider, but the basic steps remain the same:

• Log in to your domain provider and access the administration interface.
• Navigate to the DNS settings and add a new DNS TXT record.
• Depending on your specific scenario, enter the following keys:

DNS settings for individual mailbox accounts

• Add a "Hostname" entry containing the first part of the key (6) (see Figure 2).
• Create a "Target" entry and insert the second part of the key (7) (see Figure 2).
• Save the changes and wait for them to take effect.

DNS settings for mailbox family accounts (activating the domain for the entire family)

• Add a "Hostname" entry containing the first part of the key (8) (see Figure 3).
• Create a "Target" entry and insert the second part of the key (9) for the administrator (see Figure 3).
• Save the changes and wait for them to take effect.

After a short technical waiting period, you will be able to create additional aliases for this domain. No further DNS configuration will be necessary.

Copy Carefully

When copying cryptographic keys or their components, make sure that no characters are lost or altered. Ensure that you copy the entire key correctly and that no changes occur through the clipboard.

Notation in the Domain Name System

Depending on the provider, different notations may be used for DNS entries. Please refer to your provider’s documentation or support to learn which format is required. Common notations include:

• p30oe995fc9105322345b6277ac3b1i2eb45106j5j7.example.com. (with trailing dot)
• p30oe995fc9105322345b6277ac3b1i2eb45106j5j7.example.com (without trailing dot)
• p30oe995fc9105322345b6277ac3b1i2eb45106j5j7 (only the first part without dot and domain)

Waiting Time – DNS Updates

The worldwide synchronization of the DNS entry can take up to 24 hours. Only after mailbox can retrieve the change can you add the new mail address as an alias. This waiting time is technically necessary and cannot be accelerated.

Further tools to check the progress can be found under "Troubleshooting" later in this article.

Step 3: Add the mailbox MX Records in the DNS Settings of Your Domain Provider

Now you need to add an entry in the Domain Name System that ensures mails sent to your domain alias are routed to the mailbox servers. Another DNS entry, the so-called MX record, is required for this. You can also adjust this in the DNS settings of your provider.

You can find the necessary data for this in the mailbox settings. Simply open the menu from Step 1 of this guide again to retrieve the data (see Figure 1).

Note: If the configuration of the DNS entries was successful, you will now see the following message there:

Figure 3: Some of the images in this article are currently being updated or added. We're working to provide the missing screenshots as soon as possible. Thank you for your patience and understanding!

The three highlighted lines contain all the information you need for the configuration at your provider:

• the name of your domain (12)
• the priority of the forwarding (13)
• the destination of the forwarding, i.e., the future responsible mail servers (14) at mailbox.org

As you can see, three different mail servers are defined at mailbox. If one of them fails, the other servers automatically take over – this ensures that our services remain available to you.

Mail Server Priorities in DNS

For this to work reliably, mxext3.mailbox.org must have a lower priority than the other two entries. Therefore, you will find the value "20" (13) in this line, while the other servers have the value "10".

How to configure the MX records

1. Log in again to the administration interface of your domain provider and navigate to the settings for the Domain Name System (DNS).

2. Add an "MX record":

   • Enter your domain name under "Host" or "Hostname" (12), for example, example.com..
   • Please note the information about notation in the info box "Notation in the Domain Name System" further up on this page.

3. Enter the "Priority" or "IN MX" value (13).

4. Enter our incoming mail servers as the "Destination" or "Points to..." value (14).
   Again, follow the notation required by your provider.

5. Save the record.

Repeat these steps for all three entries (see Figure 4)

Make sure that:

• Your domain (12) is entered identically in all three lines in the left column.
• The entry mxext3.mailbox.org has the priority 20 (middle column, third row) – (13).
• All MX records that do not point to the mailbox servers have been removed.
• The notations meet your provider's requirements.
• The changes have been saved.

From now on, you can also send emails from your own domain via mailbox.

The correct order

The order of these steps is very important:

1. First, create the required aliases in mailbox.
2. Then, change the MX records at your domain provider.

Important: As soon as your MX records point to our servers, mailbox will receive all emails for your domain.
If the respective target addresses are not set up as aliases with us, these emails will be automatically rejected as undeliverable ("User unknown").

If you have already used the email addresses before, please check your old mail inbox, as emails may still arrive there until the DNS synchronization is successfully completed.

Only after a few hours – in some cases up to 24 hours – will it be known worldwide that mailbox is now responsible for your email addresses.

Step 4: Optimize Spam Reputation in DNS

To ensure that as few of your sent emails as possible end up in your recipients' spam filters, you should also apply the following settings.
The table contains examples of DNS records that you need to configure with your provider to properly set up SPF, DKIM, and DMARC.
Replace example.com with your domain and postmaster@example.com with your own email address.

Detailed DNS Configuration

You can find more details about the necessary settings in the article
SPF, DKIM, and DMARC: Improve Spam Reputation and Avoid Bounces

DNS Records for Your Domain

Hostname	Record Type	Target	Protocol
@	TXT	v=spf1 include:mailbox.org ~all	SPF
MBO0001._domainkey.example.com	CNAME	MBO0001._domainkey.mailbox.org.	DKIM
MBO0002._domainkey.example.com	CNAME	MBO0002._domainkey.mailbox.org.	DKIM
MBO0003._domainkey.example.com	CNAME	MBO0003._domainkey.mailbox.org.	DKIM
MBO0004._domainkey.example.com	CNAME	MBO0004._domainkey.mailbox.org.	DKIM
_dmarc.example.com	TXT	v=DMARC1; p=none; rua=mailto:postmaster@example.com	DMARC

Special Cases

• If you own multiple mailbox accounts, you must add the individual mailbox security key for each account in the DNS management of your domain.
  → This requirement does not apply to family accounts.

• A mailbox account can be linked to multiple own domains.

• It is possible to use a domain in both a business and a private customer account.

• The secure sending address @secure.mailbox.org is not available for own domains.

• mailbox does not count aliases for the usernames postmaster@, abuse@, hostmaster@, and webmaster@.
  → However, these must be created before reaching the maximum number of aliases.

• Some DNS providers do not allow entries with the same priority.
  → In this case, use descending priorities like 10, 20, and 30.
  → mxext3.mailbox.org must then have the lowest priority (30).

Troubleshooting 1 – Different DNS Settings at Your Provider

Example: Hetzner

At the provider Hetzner, you need to enter the first part of the key including the domain name with a trailing dot into the field "Hostname*" (15).
The second part of the key is entered in the input field "Target*" (16) (see Figure 5).

Figure 4: DNS settings at Hetzner.

If you want to create the MX records from step 3, this is done in this dialog at Hetzner.
Here, enter the hostname under "Hostname" (17), the priority of the respective entry under "Priority" (18), and the MX servers from mailbox.org under "Target" (19) (see Figure 6).

Figure 5: MX entries at Hetzner.

Example: Inwx

This is what the dialog for DNS settings looks like at the provider Inwx.
The application uses "Name" (20) and "Value" (21).
Inwx does not require the additional specification of the target domain (see Figure 7):

Figure 6: DNS entries at INWX.

Example: Netcup

In the input masks of the provider Netcup (see Figure 8), for example, it is not necessary to specify the top-level domain.
Here you only need to enter the first part of the key, without example.com and without a trailing dot, into the input field "Host" (22).
As "Destination" (23), please enter the second part of the key (see Figure 8):

Figure 7: DNS entries at Netcup.

Troubleshooting 2 – Query DNS Records via Command Line

Linux and macOS users can also use the dig command via the terminal. In the "ANSWER SECTION" of the command output, you will find the necessary information.

dig example.com mx

; <<>> DiG 9.11.3-1ubuntu1.13-Ubuntu <<>> example.com mx;; global options: +cmd;; Got answer:;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 22604;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 1;; OPT PSEUDOSECTION:; EDNS: version: 0, flags:; udp: 65494;; QUESTION SECTION:;example.com. IN MX;; ANSWER SECTION:example.com. 3600 IN MX 10 mxext1.mailbox.org.example.com. 3600 IN MX 10 mxext2.mailbox.org.example.com. 3600 IN MX 20 mxext3.mailbox.org.;; Query time: 67 msec;; SERVER: 127.0.0.53#53(127.0.0.53);; WHEN: Fri Aug 28 11:51:15 CEST 2020;; MSG SIZE rcvd: 118

Windows users can run this command in the command prompt (cmd.exe):

nslookup -querytype=MX example.com

Server: UnknownAddress: 192.168.179.1 Nicht autorisierende Antwort: example.com MX preference 10, mail exchanger mxext1.mailbox.org example.com MX preference 10, mail exchanger mxext2.mailbox.org example.com MX preference 20, mail exchanger mxext3.mailbox.org

Summary

In conclusion, it is important to correctly configure the DNS records when setting up email addresses with your own domain and to carefully follow the entire process. Make sure to properly insert the security keys into your domain's DNS settings and to set the correct MX and TXT records to ensure smooth usage of your email address. Regularly check whether the changes have been successfully applied, and follow the recommended best practices to improve your spam reputation and optimize email deliverability.