DACH (Germany, Austria, Switzerland) consumer email is split unevenly across providers. Gmail and Outlook hold the professional inbox, but the consumer side is dominated by local players: GMX and web.de (both United Internet), and T-Online (Deutsche Telekom). Senders optimising only for Gmail consistently underperform here.
Treat United Internet (GMX, web.de, 1&1) as one filter and T-Online as another. Pass strict SPF, sign with DKIM aligned to your From-domain, get on the CSA whitelist if your volume justifies it, and translate marketing copy into German rather than relying on auto-translate-flavoured English. Greylisting is normal — design for retries.
United Internet (GMX, web.de, 1&1, mail.com)
GMX, web.de, mail.com and the 1&1 mailboxes share a single filter stack. Reputation built at one applies across all. Notable behaviours:
- SPF strict: SPF softfail is treated more harshly than at Gmail.
~allis OK,?allis risky, missing SPF is near-instant Spam. - Greylisting: first-time senders to a given recipient often get a 4xx temp-fail. Retry behaviour from your MTA matters — bursty senders that do not retry within 15-30 minutes lose mail outright.
- Volume ramp: aggressive volume jumps (e.g. 10x daily volume increase) get throttled. Spread ramps over two weeks minimum.
T-Online (Deutsche Telekom)
T-Online runs an older but still meaningful filter. It is stricter on SPF than United Internet and slower to update reputation in either direction:
- SPF as a hard gate: SPF fail is reject, not Spam. SPF softfail still routinely lands in Spam.
- FCrDNS (forward-confirmed reverse DNS) is checked. Sending from an IP without a matching PTR is a near-instant downgrade.
- Recovery is slow. Once T-Online has a negative impression, it takes weeks of clean traffic to recover, not days.
The CSA whitelist (Certified Senders Alliance)
The CSA is the single most useful institution in DACH deliverability. Both United Internet and T-Online honour it: listed senders bypass parts of the content filter and get stricter monitoring instead. Membership is paid (annual fee + usage component) and requires a clean operational record. For a sender with serious DACH volume it is the cheapest lift available; for a small sender it is unnecessary.
Content and language
- German content from a non-DE domain is treated more strictly than the same content from a
.desender. Not because the TLD itself is a ranking signal, but because filter operators see unaligned-language traffic as more likely to be spam. - Auto-translate flavour (literal English syntax in German words) is itself a content signal. A professional translation is part of deliverability, not marketing.
- Unsubscribe must be in German for German-language mail. Both List-Unsubscribe headers AND a visible link with German wording. Mixed-language unsub patterns trigger penalties.
Authentication recipe for DACH
- Publish SPF with strict
-all. Keep DNS lookups under 10. - DKIM-sign with a 2048-bit key,
d=aligned to your From-domain. Both T-Online and GMX accept ARC-validated DKIM, but native alignment is faster. - DMARC
p=rejectwhen ready;p=quarantineat minimum if you target DACH. - PTR record on your sending IP that resolves forward to the same hostname. Non-trivial for shared-IP ESPs — verify before sending volume.
How to test placement at GMX and T-Online
Neither provider exposes a Postmaster Tools equivalent. The only way to know your placement is a direct seed test. Our free inbox placement test includes both GMX and T-Online seeds — pick them at the start, send one email, and the report shows folder placement plus parsed authentication results from each provider. The Authentication-Results header text from T-Online in particular is more diagnostic than what Gmail returns.