Yes. You can verify any @1und1.de address in real time with a direct SMTP handshake that provides 99.7% accuracy. 1und1.de is operated by 1&1 Internet, runs 2 mail servers, enforces 2 of 3 authentication standards, and is currently responding to SMTP.
Every check returns one of three clear outcomes so you know exactly what to do with the address.
The mailbox exists and accepts mail. Send with confidence, the address is deliverable.
The mailbox does not exist, is disposable, or will hard-bounce. Remove it to protect your sender reputation.
The server is catch-all or greylisting, so existence cannot be confirmed. Send selectively and watch engagement.
1und1.de publishes 2 MX records. The primary mail exchanger is mxint01.1and1.com, hosted by 1and1.com, and it is currently reachable and answering SMTP. Mail is routed through these servers in priority order, lowest number first.
| Priority | Hostname | IP | Status |
|---|---|---|---|
| 10 | mxint01.1and1.com | 212.227.17.16 | Reachable |
| 10 | mxint02.1and1.com | 212.227.17.17 | Reachable |
220 mxint.1and1.com (mxcorp001) ESMTP Tue, 02 Jun 2026 12:11:10 +0200Yes. 1und1.de is a valid email domain, operated by 1&1 Internet. Addresses are persistent and real mail reaches a genuine recipient. Individual mailboxes still go stale, so verify each one before you send.
A live SMTP handshake connects to 1und1.de's mail server and asks whether the mailbox exists using the RCPT TO command, without ever transmitting a message. The recipient never sees the check.
Each address runs through 30+ checks including SMTP existence, catch-all detection, role-account filtering, and disposable matching. The same engine has verified billions of addresses since 2012.
Every unverified address is a gamble. Here is what happens when you skip verification and mail a list that has not been cleaned.
Free inboxes get abandoned constantly. Verification drops the dead 1und1.de mailboxes before you mail them.
Mistyped 1und1.de addresses fail a real SMTP check, so they never turn into a hard bounce.
A clean list keeps your bounce rate low, and a low bounce rate is what protects inbox placement on a big send.
Mailing only live 1und1.de addresses raises every rate that matters: opens, clicks, and replies.
1und1.de is 1&1 Internet.
1und1.de is a German ISP email domain from 1&1 Internet, part of United Internet AG headquartered in Montabaur, Germany. 1&1 provides broadband, hosting, and email services to millions of German consumers and businesses.
1und1.de implements SPF, DKIM, and DMARC authentication. United Internet maintains robust anti-spam infrastructure across its brands. The service complies with German and EU GDPR regulations.
The 1und1.de mail servers enforce recipient verification and reject invalid addresses. The domain does not operate as catch-all. German ISPs apply strict rate limiting and reputation-based filtering.
For delivery to 1und1.de, authenticate with SPF, DKIM, and DMARC. German providers are among the strictest. Comply with German UWG anti-spam rules for commercial messages.
Upload a CSV or TXT list of 1und1.de addresses to the bulk email verifier. Every address runs through a live SMTP handshake plus catch-all, role-account and disposable detection, and you download a clean list when processing completes. For real-time checks at signup, use the real-time email verification API.
CSV or TXT with one email per line. No formatting needed.
Each 1und1.de address is checked with a live server handshake.
Get a verified list with status codes, risk flags, and catch-all detection.
Pay as you go. No subscriptions, and credits never expire.
Everything about verifying email at this domain.
Yes, 1und1.de is a valid email domain provided by 1&1 Internet to its internet subscribers. It is a legitimate ISP-issued email address.
No, 1und1.de is not a disposable or temporary email provider. It is an ISP-provided email service tied to an internet subscription from 1&1 Internet.
1und1.de uses mail servers operated by 1&1 Internet. Check the MX records section above for specific server details and authentication configuration.
Yes, you can send marketing emails to 1und1.de addresses with proper opt-in consent. ISP email providers apply spam filtering, and addresses may become inactive if subscribers cancel their internet service. Regular list verification is recommended.
Use BulkEmailChecker to verify 1und1.de addresses via SMTP checks. ISP domains may have specific rate limiting or greylisting behaviors. Our tool handles these provider-specific configurations automatically.
Upload a CSV or TXT list to the bulk email verifier. Every address runs through 30+ checks including SMTP existence, catch-all detection, role-account, and disposable matching. Processing time depends on list size.
99.7% accurate using a direct SMTP handshake with 1und1.de's mail servers, the same engine that has verified billions of addresses since 2012.
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