Hornetsecurity offers the possibility to set up domains including umlaut. The domains will be added through the Control Panel using the tab Settings > Domains > Add domain.
For the system to be able to interpret the umlaut, it will need to be converted to an ACE-String. You will find a converter from the following website:
https://www.denic.de/en/service/tools/idn-web-converter/
You will need to add the converted domain to the Control Panel. Adding a domain including an umlaut into the system will result in declined emails, as the spam filter will not be able to assign the incoming emails to the appropriate customer.
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