I have a problem with using a federated ID

Support intro

I have two nextclouds on two Ubuntu servers with IP addresses of and

In nextcloud on, I am going to share a file with the user test of nextcloud on I filled in my federated ID in the share box: test@ , but sharing failed.

What causes this? I won’t support it user@IP Is the address in this format? I hope you can help me. Thank you very much!

Nextcloud version (eg, 18.0.2):
Operating system and version (eg, Ubuntu 20.04):
Apache or nginx version (eg, Apache 2.4.25):
PHP version (eg, 7.1):