T-Online mailbox provider

According to Live Direct Marketing's daily Tranco top-1M scan (July 13, 2026), T-Online is the mailbox provider for 10 domains — 0.00% of 658,711 domains with MX records. Detection method: primary MX record (lowest preference).

Key facts

T-Online is the email and web hosting service operated by Deutsche Telekom, Germany's largest telecommunications provider. It serves as a primary mailbox platform for users across the German-speaking regions and is a foundational element of the German internet infrastructure.

T-Online's prevalence in the Tranco top-1M dataset skews heavily towards high-traffic, enterprise, and well-known sites concentrated in the .de namespace. For senders and organisations managing email to German recipients or hosting on German infrastructure, T-Online's filtering and acceptance policies represent a critical touchpoint; its prominence means that deliverability failures to T-Online will likely affect a significant portion of any German-focused mail stream.

Where T-Online sits in the Tranco ranking

Tranco rank bandDomainsShare of its base
Top 1,000110.0%
Top 10,000110.0%
Top 100,000110.0%
Top 1,000,000660.0%
Unranked110.0%

Top-level domain split

TLDDomainsShare
.de770.0%
.eu110.0%
.net110.0%
.org110.0%

T-Online's role in German market mail flow

Because T-Online appears as the primary MX for many high-traffic and established German sites—rather than just consumer domains—organisations sending into the German market must account for T-Online's acceptance criteria as a distinct segment within their deliverability strategy. Testing and monitoring T-Online delivery separately from other European providers is essential for verifying that mail from your infrastructure reaches German recipients reliably, particularly when those recipients are affiliated with enterprise or well-known domains.

See the full T-Online data page (KPI cards, trend, sample domains) →

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Frequently asked questions

Should I test email deliverability specifically to T-Online?

Yes, if you send to German recipients or domains in the .de namespace; T-Online's concentration among high-traffic and enterprise sites in Germany makes it a primary barometer for German mail deliverability.

How many domains use T-Online?

10 domains in the Tranco top-1M use T-Online as their mailbox provider as of July 13, 2026 (0.00% of domains with MX records), according to Live Direct Marketing's daily DNS scan.

Is T-Online common enough to affect email deliverability testing?

T-Online accounts for 0.00% of domains with MX records in the top 1M. Whether you should seed a test mailbox there depends on how much of your audience it represents — the co-usage table above shows the services it appears alongside most.

Which countries or TLDs use T-Online most?

T-Online's largest TLD is .de (70.0% of its domains); it appears across 4 TLDs in total.

Other mailbox providers

Self-Hosted (22.44%)Google Workspace (21.79%)Microsoft 365 (16.74%)Unknown / Other (7.54%)Generic / unmatched (mx*.*) (2.57%)Proofpoint (1.90%)Generic / unmatched (mail.*) (1.75%)Yandex 360 (1.64%)Cloudflare Email Routing (1.60%)Mimecast (1.52%)