Stricter rules for accepting mail with sender

Mail from senders with the domain is rejected with the following error message:
Forged sender domain from this server

This means that this mail was not delivered via the official Bluewin servers. Bluewin determines by an SPF entry from which servers legitimate mails with sender should come. Cleanmail has so far accepted mail with sender from any server, but now implements the Bluewin specification. With this measure sender falsification and phishing attempts are prevented.

The recipient can not circumvent this rejection by creating an entry in the white list. Instead, the sender must use the correct outgoing mail servers operated by Bluewin. You will find the necessary information in the Swisscom Help Center. If you have any questions about the configuration, please contact Swisscom support or your local PC supporter.


Februar 1st 2019 is “DNS-Flag-Day”.

The Domain Name System DNS is the contact app of the Internet. It allows you to view this website by entering the name “” into the address bar of your browser, and ensures that emails with are delivered to the right mail server(s).

In the last decades, the DNS protocol has been in constant evolution. Unfortunately there are still quite a lot DNS servers which are still on pre-1999 levels on how they understand the DNS protocol. Current DNS server software uses a series of workarounds to ensure that such aged software still works.

On February 1st 2019 many large providers will turn off these workarounds. Even though 20 years of lead time should be sufficient, and even though there are publicly available tools to check the status of one’s own DNS server, some services and service providers will be surprised on this day.

If you encounter unexpected outages on or after February 1st 2019, there is a certain probability that this is due to the “DNS-Flag-Day”. The infrastructure of Cleanmail is on current levels and thus not affected by this change. However, it could well be that other organisations are affected with the result that they can not send emails to us, or that they can not receive emails sent through us. Please note that this behaviour is outside of the control of Cleanmail and can thus not be whitelisted.

Additional information on the DNS-Flag-Day can be found at


Outlook Express End-Of-Life

Mail is rejected with error message:

Cleanmail no longer accepts messages created by Microsoft Outlook Express. Microsoft ended support in 2009 and replaced it by Windows Mail

This software has not received any security updates for more than 9 years, its use is strongly discouraged.

Nowadays Outlook Express, resp. headers which claim creation by Outlook Express, are almost exclusively used by spammers.

Missing mail

If missing mails are not to be found in your local spam folder or in the Cleanmail Quarantine, please contact our support dept by mail (

To track missing emails or delivery issues Cleanmail requires:

  • Sender mail log snippet showing failed transactions, connections, DNS and Internet routing issues, which ever may apply.
  • Failed sender error message / bounced email.
  • Sender, Recipient and Date of missing message.


For technical support please contact us via, and via for administrative and sales questions. The easiest way is maybe via the chat you’ll find on the bottom right (the orange square, clic, write, send, give us your contact information if you don’t get a quick anwser, thank you).

☣️ Please report missed spam as .eml attachment to

Please note that this KB is currently only available in German.

If you do not find the resolution for your request in the support database, please contact us.

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