# GMX: MX records and email verification

How GMX domains look in DNS, how GMX answers an SMTP verification handshake, and which verdicts to expect for gmx.net, gmx.de and gmx.com addresses.

Updated: 2026-09-03

GMX is one of the two big German consumer mailbox providers, run by 1&1 Mail & Media alongside its sister brand WEB.DE. It serves gmx.net, gmx.de, gmx.at, gmx.ch and the international gmx.com, all on the same platform. Spaw reports the GMX domains as `mx_provider: "gmx"`.

## How GMX shows up in DNS

GMX domains publish MX records under `gmx.net`: gmx.net and gmx.de point at `mx00.emig.gmx.net` and `mx01.emig.gmx.net`, and gmx.com at `mx00.gmx.net` and `mx01.gmx.net`. Spaw matches the `.gmx.net` suffix. WEB.DE, despite sharing the infrastructure, uses hosts under `web.de` and classifies as `other` until the classifier learns that pattern. GMX is a mailbox host: `mx_found` is true and `mx_implicit` is false.

## How GMX answers a verification handshake

GMX rejects unknown recipients at `RCPT TO`, so a missing mailbox is confirmed in the session. The provider is strict about who it talks to at all: it enforces reverse DNS on the connecting host, applies reputation checks before the recipient step, and greylists or refuses connections from sources it does not trust. A probe from infrastructure GMX has not seen is therefore more likely than average to end with `smtp_reason: greylisted` or `no_connect` rather than an answer.

## What that means for your verdicts

Confirmed answers are `deliverable` with `mailbox_exists: true` or `undeliverable` with `reason: mailbox_not_found` and `smtp_reason: no_mailbox`. Unverified probes leave `smtp_checked: false` and `mailbox_exists: null`, the verdict rests on the free signals, ten risk points are added for the unverified state, and `mailbox_confidence` is returned; GMX is not on the established-provider list, so that estimate depends on the username's shape and your own delivery data more than anything else. GMX has no consumer username rules in Spaw's rule set, so `invalid_local_part` does not apply. Catch-all does not occur on consumer GMX domains.

For unverified single lookups, pass `callback_url` so Spaw re-checks after 5 and 20 minutes; for lists, report delivery outcomes so confirmed mailboxes carry `smtp_reason: delivered_recently` on later lookups.

## SPF and DMARC at GMX

Consumer GMX users have nothing to configure. The GMX domains publish their own SPF and DMARC records, and GMX enforces DMARC on inbound mail, so a message with a gmx.de From address sent through another service fails alignment. Spaw's `dmarc_policy` field shows the live policy for any domain; for gmx.net it reflects whatever GMX currently publishes.

## Practical notes for sending to GMX users

GMX and WEB.DE together receive a large share of German consumer mail and are known for strict inbound policies: a valid reverse DNS entry for your sending IPs, aligned SPF and DKIM, and a working postmaster address are practical requirements, and 1&1 operates a postmaster programme with a certification for bulk senders. Plus-addressing is not a standard feature on consumer GMX accounts. Addresses on these domains are typically individuals, so role-word usernames are rare and `reason: role` is uncommon here.

For a live look at any GMX domain, run it through the free MX lookup and the SPF and DMARC checker.

Reference: https://spaw.co/email-providers/gmx