German umlauts (ÄÖÜäöü) are allowed in URLs and email addresses for some years now, but EmEditor does not recognize them in the Link feature. The link stops right before the first umlaut.
When I try to manually add the German umlauts in the field “Link / Recognize These Characters” they don’t stick but are automatically removed.
The next version (v18.2.93) will allow you to check this option for email addresses as well as URLs. The title of this option will be changed to “URLs and Mail Addresses Can Include Half-Width Unicode Characters”.