Quick answer
How to set up Mailbox.org with your own domain?
On a Standard (36 EUR a year) or Premium plan, add your domain as an external alias to get a security key, publish it as a TXT record, then add four MX records, mxext1 to mxext4.mailbox.org at priority 10. SPF and four DKIM CNAMEs follow. Postelva registers the domain; you type these records in its DNS editor.
DNS records for a Mailbox.org custom domain
| Record | Type | Host | Value | Priority |
|---|---|---|---|---|
| Ownership | TXT | first part of your security key | second part of your security key | - |
| Mail 1 | MX | @ | mxext1.mailbox.org | 10 |
| Mail 2 | MX | @ | mxext2.mailbox.org | 10 |
| Mail 3 | MX | @ | mxext3.mailbox.org | 10 |
| Mail 4 | MX | @ | mxext4.mailbox.org | 10 |
| SPF | TXT | @ | v=spf1 include:mailbox.org ~all | - |
| DKIM 1 to 4 | CNAME | MBO0001._domainkey to MBO0004._domainkey | MBO0001._domainkey.mailbox.org. to MBO0004._domainkey.mailbox.org. | - |
| DMARC (start) | TXT | _dmarc | v=DMARC1;p=none;rua=mailto:[email protected] | - |
Steps, in the order Mailbox.org validates them
Register the domain
Buy it in the Postelva client area. Mailbox.org does not sell domains; it tells you to edit DNS where the domain is registered.
Get the security key
In your mailbox.org account open All settings, Email addresses, Email aliases, Add external alias. Enter an address on your domain and save. The first save fails on purpose and shows the key.
Publish the key as a TXT record
The host is the first part of the key, without a trailing period or the domain, and the value is the second part. Syncing can take up to 48 hours.
Save the alias again
Repeat the same step. Mailbox.org checks the TXT record in the background and confirms when it succeeds.
Switch the MX records
Add the four MX records and delete any MX that does not point to a mailbox.org server.
Add SPF, DKIM and DMARC
Publish the SPF TXT, the four CNAMEs and a DMARC policy, then send a test message both ways.
Which Mailbox.org plan allows a custom domain?
Standard at 36 EUR a year and Premium at 108 EUR a year both allow custom domains; Light does not, except inside family accounts. Standard gives 50 aliases for custom domains and Premium 250; the number of domains itself is not stated on the price page. Monthly billing exists for Standard (4 EUR) and Premium (12 EUR), while Light is sold only yearly at 12 EUR.
Mailbox.org does not accept crypto: its payment page lists PayPal, SEPA direct debit, American Express, Mastercard, Visa, bank transfer and cash by post or deposit. A reader paying everything in crypto can still buy the domain from Postelva with BTC, USDT, USDC, ETH, SOL, LTC and use another method for the mailbox.
What if my DNS host refuses four MX records at priority 10?
Use priorities 10, 20, 30 and 40, with 40 as the lowest. Mailbox.org's page gives this fallback for hosts that reject identical priorities. Equal numbers share traffic between the servers, while distinct numbers make senders try them in order; both deliver mail. The concept is in what is an MX record.
Remove old MX records before you test. Leftovers from Gmail or another host split your mail between two systems. Sync can take up to 48 hours, so keep the old mailbox open meanwhile, as detailed in how to move email to a new provider without losing mail.
How do SPF, DKIM and DMARC work on Mailbox.org?
Mailbox.org signs with four DKIM keys, named MBO0001 to MBO0004, and publishes SPF through include:mailbox.org. Each DKIM CNAME has the host MBO000N._domainkey and points to MBO000N._domainkey.mailbox.org. Keep one SPF record only; if you already have one, add the include rather than creating a second, a rule detailed in how to create an SPF record.
For DMARC, Mailbox.org suggests a starting point of p=none with a report address, then a tighter policy later. It warns that a strict policy set too early can bounce legitimate mail. The staged approach is in how to set up DMARC.
Does Postelva offer a Mailbox.org template?
No: Mailbox.org needs its records typed by hand, and the editor is built for it. Postelva provides one-click DNS templates for Proton Mail, Fastmail, Zoho Mail, Google Workspace and Microsoft 365, plus an SPF + DMARC template and a "no email" template for a domain that sends nothing, which does not include Mailbox.org. The editor supports free DNS hosting with A, AAAA, CNAME, ALIAS, MX, TXT, NS, SRV and CAA records, DNSSEC, and your own nameservers if you prefer (2 to 13).
According to Postelva's count of 12 November 2026, a Mailbox.org domain needs 11 records (1 TXT, 4 MX, 1 SPF, 4 DKIM, 1 DMARC), more than the 8 of Proton Mail and the 6 of Fastmail. A .com is $12.49/year a year, the same on renewal, and email replies within 12 hours, 7 days a week, including help with MX, SPF, DKIM and DMARC records.
Catch-all works too: create an alias of the form @yourdomain.com. Only one account can hold the catch-all of a domain, and Mailbox.org lets you block it if it floods with spam. Mailbox.org, based in Germany, makes PGP optional rather than default, so choose it for portability and a flat yearly price.
Questions about Mailbox.org and custom domains
Why does the first alias save fail?
It is the design: Mailbox.org refuses the alias until the TXT record exists and shows the security key at that moment. Publish the record, then save again.
Can the domain stay with Postelva while mail is at Mailbox.org?
Yes. Mailbox.org says to set DNS where the domain is registered, so the records live in the Postelva DNS editor.
How many addresses can I create?
Standard offers 50 aliases for custom domains and Premium 250. A catch-all covers the rest of the names.
How do I check the MX records?
Run dig example.com MX on Linux or macOS, or nslookup -type=MX example.com on Windows. Four mxext hosts should appear.
In summary
- Custom domains need Standard (36 EUR a year) or Premium (108 EUR a year).
- Get a security key from Email aliases, publish it as a TXT, then save again.
- MX: mxext1 to mxext4.mailbox.org, all at priority 10 (or 10/20/30/40).
- SPF: v=spf1 include:mailbox.org ~all; DKIM: MBO0001 to MBO0004 CNAMEs.
- 11 records in total; no Postelva one-click template, no crypto at Mailbox.org.
- Sync can take up to 48 hours: keep the old mailbox open.
Sources (4)
- mailbox.org KB - Using emails with a custom domain — mailbox.org (read 2026-11-12)
- mailbox.org KB - SPF, DKIM and DMARC — mailbox.org (read 2026-11-12)
- mailbox.org KB - Catch-all alias — mailbox.org (read 2026-11-12)
- mailbox.org prices — mailbox.org (read 2026-11-12)