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Recommendations for Sending E-mails to 1&1 Mailboxes

1&1 is committed to providing a trusted and secure service to its users. For this reason, careful evaluation of incoming e-mails and protection against unsolicited e-mails are our top priority.

The following notes apply to the operators of the delivering services:

Respect requests by recipients to stop sending unwanted e-mails
If a 1&1 user can demonstrate that you have failed to stop sending undesired e-mails despite a request to the contrary, we reserve the right to block your service permanently.

Observe the legal provisions
Observe the legal provisions that are applicable in your country. For the USA, for example, this is the Can-Spam Act. Note that senders of bulk e-mails can be held responsible if they fail to seek the consent of the recipient.

Observe the recommendations of the MAAWG working group
The Messaging Anti-Abuse Working Group (MAAWG) cooperates with large and important internet service providers to regularly draft a guide to sending e-mails that you should observe.

RFC compliance
E-mails and communications with our servers must comply with the current RFC defined standards.

E-mails not received from dial-up areas
E-mails must not be sent directly to our mail server from dial-up networks. E-mails from users with dynamic IP addresses must be sent via smart hosts or SMTP relay servers that are protected against misuse.

Reverse DNS entry
A reverse DNS entry (FQDN) must exist for the delivering server.

Correct HELO
You must send a meaningful and plausible HELO/EHLO in the sense of RFC 5321.

Sender Policy Framework
On request from a customer, we will investigate your SPF records. The sender addresses for forwarded e-mails must therefore be aliased using SRS.

Securing the sending server against misuse
The delivering server must be protected against unauthorized access.

RBL lists
We check various established RBL lists. Please make sure that your server is not on one of these lists. You can check this information at

The following rules apply for senders of bulk e-mails:

Cleaning up address lists
The sender must immediately remove e-mail addresses from their dispatch lists if hard bounces occur at these addresses. If you attempt to deliver mail to multiple unknown (or disabled) 1&1 mailboxes, you will be temporarily blocked. We also reserve the right to block you permanently in this case.

Imprint requirement
The client or contractual partner of the sender must be clearly identifiable for the recipient. We recommend including non-electronic contact information for the sender, including the telephone number and physical address, in requested bulk e-mails.

Double opt-in
Send e-mails only to recipients from whom you have received permission to receive bulk e-mails, e.g. newsletters. We recommend using a double opt-in process, for example.

The recipient must be given a fast and simple opt-out option for receiving bulk e-mails (newsletters, advertising, etc.). Each e-mail should contain a note to this effect.

Whitelisting by external service providers
As a sender of bulk e-mails we recommend that you participate in the Certified Senders Alliance. You can find more information here.