What were you trying to do that didn't work?

Postfix itself will support UTF8 for local and domain part, but not when using PostgreSQL lookups during the hard coded LATIN encoding in the source code. This is only fixed by upstream on 3.8.

But I think it will be possible to back port it to the RHEL version of Postfix with the default set to LATIN, but enable override it via the encoding option.

Please provide the package NVR for which bug is seen:

postfix-3.5.9-24.el9.x86_64

For more see:

https://www.postfix.org/pgsql_table.5.html