Best Practices

Information for service delivery operators

Follow the recommendations of M3AAWG

M3AAWG (Messaging, Malware and Mobile Anti-Abuse Working Group) is the world's largest association for combating online abuse. M3AAWG's recommendations are up-to-date industry standards and are rated as best practices in the e-mail community.

No reception of dynamic IPs

Your e-mails may not be delivered directly from dialup networks to our Mail Exchange servers. The e-mails of users with a dynamic IP address must be sent via a smart host or SMTP relay server that is secured against abuse.

Authenticate with SPF, DKIM, and DMARC

To ensure the validity and origin of your domains, we recommend that you authenticate with SPF and/or DKIM and have a DMARC record on your DNS. We respect the requirements of other domain owners and check SPF records, DKIM signatures and DMARC records. The sending addresses of forwarded e-mails must therefore be adjusted with SRS.


To protect our customers from misuse we use various real time blocklists (RBLs). If one of your domains or IPs is blocklisted, you can check under If you are listed, submit an application for the removal of the entry to the respective RBL service provider and respect the guidelines on content, sending behavior and technical requirements for future e-mails.

Secure the sending servers against misuse

Secure your servers against abuse and attacks by regularly patching and following security best-practices. As an e-mail provider, we depend on all system participants to do their best to protect themselves and out customers.

Warming up new IPs

If you are using new IPs you need to warm them up first. This helps to increase the reputation of your new IP and ensures that they are rated as safe by the receiving service providers. To do this, start sending a small number of emails each hour, then you can begin to increase the hourly total to build your IP reputation.

Information for bulk e-mail senders

Distribution lists

It is best to only use distribution lists that you have created yourself and not use lists that you have received from an external source. Your reputation with e-mail providers decreases if you use invalid or inactive email addresses. Therefore, check your distribution lists regularly and ensure you maintain your e-mail lists in terms of unsubscribers, bounces etc..


We recommend that you formulate the subject line in a comprehensible and content-appropriate manner. This prevents your e-mails from being deleted directly or marked as spam.

Items in newsletters and mass e-mails

To increase the hit rate of your e-mails, it's worth checking that items like hyperlinks and attachments don't contain unwanted content that could be marked as spam from users.

Opt-in method for verifying e-mail addresses

To ensure that a customer has actively signed up for your e-mail newsletter or bulk e-mail, it is helpful to apply an opt-in method. In order to obtain clear consent, we recommend the double-opt-in method, where you have the e-mail address verified by the user.

Sending time

Make sure you send your e-mails at a reasonable time so that the e-mails are not perceived as spam and marked as such.

Separate newsletters and promotional e-mails from administrative e-mails

Use different sender addresses for newsletters and promotional e-mails than for direct customer contact.


We recommend a certification by industry recognized companies and committees like Return Path or CSA. The purpose of this certification is to ensure that your domains will be written on a comprehensive wantlist and that your e-mails are delivered to your inboxes with a higher probability.

Enter a real postal address and valid phone number in all your e-mails. The recipient of your e-mails must be able to contact you in a non-digital way.


Provide a highly visible way for a recipient to unsubscribe from your newsletters or promotional e-mails (opt-out method). Ensure unsubscriber addresses are removed promptly from your distribution lists.