Yeah, I tried that. I get a different error as a result:
Found this thread with the same error, but
SRS_SECRET = ${readfile{/etc/exim4/srs.conf}} is already in the config.
I want to make it clear again. Exim4 is installed and configured by HestaiCP on a clean Ubuntu 22.04. No manual changes have been made to the configs. And the mail server is not working.
Maybe there is a possibility to connect an external repository to update Exim4 to the latest actual version? As it is done by the panel with mariadb and nginx?
Maybe that would help to solve the problem?