Ensure you use your valid e-mail address as the envelope sender "mail from" to avoid receiving any bounce e-mails.
Ensure that the e-mail coding complies with the standards. The size relates to the entire e-mail, i. If the recipient has set up e-mail forwarding, your e-mail will be forwarded there.
You may receive a bounce e-mail from another provider after a few minutes. Please check this message and note that Telekom cannot resolve any errors that this other provider may have.
If your e-mail meets all the requirements and yet still does not arrive, you can find further tips under "Checking the SMTP dialog".
Greylisting is generally understood to mean that every incoming e-mail is initially rejected temporarily and only accepted after a renewed delivery attempt.
This is based on the assumption that only authorized e-mail systems initiate renewed delivery of rejected e-mails. As greylisting cannot actually identify unauthorized e-mails and also hinders the delivery of legitimate e-mails, Telekom systems do not use this procedure.
The Sender Policy Framework, SPF for short, can enable a check to determine whether the sending IP address is authorized to send e-mails for the domain in question.
This procedure has numerous vulnerabilities that cannot be compensated for, including those that are described here.
Therefore, Telekom does not use SPF either passively when receiving e-mails or actively for sending by creating corresponding DNS resources.
Until now, we have neither used nor evaluated DKIM signatures. Such information is always treated as strictly confidential.
We require mail server operators to take account of the recommendations provided in the "Practical tips for senders of e-mails" section, if appropriate.
In particular, it must contain an e-mail address as an abuse contact for the operator. Alternatively, it must contain an e-mail address for the provider if the IP address in question is not delegated to the mail server operator.
We expect you to treat the resources provided with as much respect as possible. We reserve the right to temporarily restrict receipt of e-mails from the IP addresses concerned in the event of unusual traffic volumes, or to suspend receipt in the event of permanent faults.
The automated use of an external blacklist always carries the risk of also preventing legitimate communication. Even though the term "blacklist" suggests a black and white judgment, it is advisable to use several criteria.
You should at least remove known e-mail services from automated filtering by using your own whitelist. Use extreme caution when selecting any external blacklist that you plan to use.
To counteract any unwanted blacklisting, either maintain your own whitelist or integrate an external list, such as the DNSWL. Of course, our servers that send e-mails are also listed there.
Only through proactive management of the blacklists and whitelists you use can you ensure that your users actually receive the desired e-mails.
Ensure that your servers are not set up as open proxy or open relay and that they do not forward any e-mails that you receive from open relay or open proxy connections.
Always keep your software up to date to prevent misuse of your resources and protect yourself against damage to your good reputation.
Use filters for outgoing e-mail as well to reduce the dispatch of junk mail spam and e-mails containing viruses.
Do not use Sender Address Verification to check that the sender addresses of incoming e-mails exist. The procedure used is not standardized and it is not possible to distinguish this procedure from, for example, that of a spammer who "washes" his address list.
It is vital to avoid what is known as "backscatter" by rejecting incoming e-mails to non-existent recipients in the SMTP dialog; furthermore, your content filter against junk mail must also not generate any bounce e-mails non-delivery notifications.
This means that filtering must be performed before an e-mail is received so that it can be rejected if necessary. For information on how to configure this, please see the documentation for your mail server.
You can find guides for Exchange, for example, at hhttp: The SMTP protocol defines response codes that provide information on the status and the recommended next steps.
If error messages occur regularly or even permanently, these indicate errors that should be analyzed in more detail urgently. Checking your SMTP logs is always the basis for further measures.
We try to output sufficiently descriptive error messages. If you need our support in eliminating errors, we ask that you attach suitable extracts from the log files to your communication.
Without the original error message, we cannot investigate the error. If e-mail delivery to your server is frequently delayed with a temporary error " Maximum parallel connections for your IP-Address reached" , this means that the delivering server has established too many connections to our server at the same time.
Therefore, when your system receives the error message, there are already multiple connections that are being used to transfer e-mails.
Please configure your mail server s so that a new connection is not established for every e-mail, and the number of messages to be transferred via one connection is not restricted unnecessarily.
If you have received a 5xx-SMTP error message: Check your e-mail queues to see if there is any unusual sending behavior or even a permanent fault.
In these cases, acceptance of e-mails from the IP addresses concerned is temporarily restricted or even permanently suspended. Therefore, ensure that your e-mail systems comply with these standards.
If you frequently receive the error message " The error message specifies a dedicated contact partner for any e-mails that are incorrectly categorized as spam.
Resume delivery only once the problem has been resolved! If you have received a 4xx-SMTP error message: An unusually high load on the Telekom servers can temporarily result in the error message "System temporarily unavailable".
Please accept our apologies for this. Such a fault is rare and is corrected promptly by our technicians. In the event of interruption to communication at IP level: To determine the cause of a serious fault, the following questions must be answered: Can your systems access the t-online.
If your server is attempting to deliver encrypted e-mails, please check whether the TLS handshake is successful correct certificate, DANE.
To be able to provide reliable information on the fault in question, it is recommended that you carry out the tests necessary to answer these questions and note the correct order.
We have described the procedure in detail under "IP troubleshooting - troubleshooting at IP level". A block may be in place, in particular, if you want to use an IP address that you have not previously used for sending e-mails; this may therefore have been caused a long time ago.
With some MTAs, the relevant error message may not appear on your system because the t-online. If you have resolved the problem that caused the error or do not believe there is a problem, please contact the dedicated contact person specified in the error message.
You can also reach this person via any of our listed systems. Alternatively, you can use our online form to contact us.
We expect all ISPs that deliver e-mails to our servers to use suitable anti-spam technologies to minimize spam. Please resolve the existing problem and then contact the dedicated contact person specified in the error message.
Telekom does not offer external access to its in-house mail filters and mail filter technologies. Telekom does not offer any whitelisting.
If you are blocked and believe that there is no longer cause for this, please contact the dedicated contact person specified in the error message.
You can also reach this person via any system that is otherwise blocked for e-mail delivery. In cases in which there are frequent, temporary blocks, the cause is often one of the following: Delivery of "backscatter" Use of "Sender Address Verification" No spam filter for outgoing e-mails No or insufficient abuse management If none of the above applies, but your server is still frequently rejected temporarily, please send an e-mail to our postmaster see the next item for more information , specifying the IP addresses of your systems that deliver e-mails.
You can reach our postmaster at postmaster t-online. Errors reported to Telekom are dealt with promptly. If high loads should occasionally lead to delays, please accept our apologies.
Furthermore, we do not send confirmation of receipt; if necessary, we will get back to you. Please understand that we cannot provide any information on the processing status for a specific customer, due to data privacy reasons.
You can find the IP ranges of the dial-ups and the IP addresses of the t-online. We expect senders of bulk e-mails to take account of the recommendations provided in the "Practical tips for e-mail senders" and "Notes for mail server operators" section, if appropriate.
For more information to help you optimize your e-mail communication and avoid confusion with unwanted spam, see the links below: E-mails and newsletters sent automatically must also offer all addressees the option of directly opting out in the e-mail concerned.
To deliver mass commercial e-mails, in particular, you require the explicit and personal! For practical reasons, this agreement to receive a particular e-mail is obtained almost exclusively by means of double opt-in procedures.
In , the German Federal Court of Justice judged opt-out only procedures to be illegal in Germany. Therefore, please delete or block all e-mail addresses