Authenticate login to Nextcloud local install to smtp server

I’m running an exim server for which I replaced the SSL/TLS certificates yesterday. I had problems doing so but the mail services is up and running. SASLAUTHD is installed and working, the test apps work fine.

I have a local install of Nextcloud and I authenticate the login to it through it’s webserver but authenticate against the smtp server that’s running SASLAUTHD.

This remote login stopped working when I changed my certs on the exim server. Log files just give ‘PAM auth error’ message.

It is not at all clear to me where I can configure the Nextcloud server to authenticate remotely to another server so I can check the SSL/TLS settings.

Can anyone point out the configuration file or procedure?

Many thanks