To use domain names with umlauts or accents (known as IDN domains = Internationalized Domain Names) as web addresses (URLs) or email addresses, several technical requirements must be met:
An IDN-compatible registrar (e.g. Webland.ch)
An IDN-compatible provider (e.g. Webland.ch)
IDN-supporting software on the end user’s device (e.g. browser or email program)
All three of these requirements must be fulfilled.
If any of them are missing, your website or mail server may not be accessible.
To ensure that everyone can access your homepage with umlauts, the local software (browser) of your visitors must also support domain names with umlauts.