Meet the New E mail Supply Necessities


What has changed at

In recent weeks, a major mailbox provider in Germany, announced some major changes to the way it accepts emails. The short version of these changes is as follows:

In order for e-mails from to be accepted, the sender must have full domain registration about their Sender Policy Framework (SPF), Identified emails with domain keys (DKIM)), Reverse DNS (rDNS) and From domains.

This means when you send an email from

  • Your SPF domain (also known as Return path domain) must be or a subdomain of This is configured automatically after the setup Domain authentication.
  • Your DKIM domain must be or a subdomain of This is also configured automatically after the setup Domain authentication.
  • The rDNS of your sending IP (s) must be or a subdomain of You can set up reverse DNS for your sending IPs by following the instructions Here.

Your domains in SPF, DKIM and rDNS must all match for to accept your emails.

What should you watch out for when sending to

When you send emails to recipients at, check your event webhook data or your email activity feed for block events from for the following reason: “554 IP = – A problem has occurred. (Ask your postmaster for help or contact for clarification.) ”

What should you do to comply with T-Online’s guidelines?

Due to the changes made by, many senders are increasingly blocked when sending e-mails to recipients from Here are some steps you can take if you find that your deliverability rates for are falling, or you notice an increase in delays or blocks.

I am using a dedicated IP address and is blocking my email.

I use shared IP addresses and blocks my email.

There is no solution to this problem for senders who want to stay on shared IP addresses. Unfortunately, has implemented a number of requirements that are fundamentally incompatible with joint IP transmission. The negative effects of these changes are not limited to SendGrid customers. They are felt by everyone Organization that uses shared IP addresses to send messages to recipients of, regardless of their email service provider.

If communication with your recipients is of vital importance to your business, we recommend upgrading to a dedicated IP address and then configure it Domain authentication and custom rDNS to achieve correct alignment.

I have dedicated IPs but I am sending emails from different domains.

The requirements of are clear: If the domain in the From address does not match the SPF, DKIM and rDNS domains, the email will be rejected. In some cases, senders can be set up IP pools to fix this problem. When you create IP pools, you can specify which IP pool a message should go through. If you create a pool for each of the domains you are sending from and the rDNS of the IPs in those pools match the domain in the sender address, you can deliver your email successfully.

In other cases where the number of different sending domains is large, it may be impossible to successfully send emails to Remember: tThe only way to get your emails is to have full alignment with your From domain across your SPF, DKIM, and rDNS domains.

My e-mails are blocked by, but none of the above statements apply to me.

If you find that your email is being blocked by and you are sure that you have full domain alignment, you need to check that postmaster site and make sure you follow all recommendations, best practices, and requirements.

Next steps with

It is likely that the changes made by have an impact on the ability of some of our customers to reach recipients on Even if you do not see any effects on your delivery to due to these requirements, we recommend completing the domain authentication and reverse DNS with your dedicated IP addresses in order to ensure optimal e-mail delivery to your recipient mailbox providers .

To learn more about email delivery and authentication best practices, see the following resources:

We will continue to monitor developments and updates of and update this article if significant changes are made.

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