Re: [exim] SMTP 550 user not authorized.

>
> hostlist relay_hosts = net-lsearch;/etc/virtual/pophosts : 127.0.0.1
>
> hostlist whitelist_hosts = lsearch;/etc/virtual/whitelist_hosts
>
> hostlist whitelist_hosts_ip = net-lsearch;/etc/virtual/whitelist_hosts

in your acl I do not see the sections that refer to these lists of
authorised hosts.
If these accept lines do exist, might it be that these clients have
changed IP or that the
/etc/virtual/pophosts file is not correctly updated anymore?

Why don't you look in your logs for the rejections?

(Besides, user not authorized does not appear to be a message that
your exim would give)

Giuliano