Forum OpenACS Q&A: URL redirects produces an error "page isn't redirecting properly"

I have only been modifying SMTP mail lite and the smtpdport value.

There is no section "SMTP mail lite".
I can exclude that updating the values for the Tcl variable "smtpdport" and updating the "acs-mail-lite" section will cause a redirection loop. Maybe, you introduced a syntax error?

Concerning "untrusted host header field":

1. Firstly, set "hostname" in the configuration file to the hostname you want to use (in your case, i would assume, this is "celtic-arts.org").
2. in case you are connecting to the same instance with multiple different host names, NaviServer allows you to specify alternative host names in the driver section (e.g., ns/module/http/servers). You can do this
   • manually, by editing the configuration file, or
   • by providing multiple values to the "hostname" variable in the configuration file (see [1])
   For you, i do not see a need to specify "whitelistedHosts" (an example is in the GitHub repository of NaviServer, [2]). The log message should be improved to say, that in case, you have properly configured the "ns/module/*/servers" section, you might use this as the last resort, when the host header field does not match any driver configuration.

hope this helps
-g

[1] https://github.com/naviserver-project/naviserver/blob/release/4.99/openacs-config.tcl#L24
[2] https://github.com/naviserver-project/naviserver/blob/main/openacs-config.tcl#L890