Redirect users to a sharepoint using 302

you could try something like this

when HTTP_REQUEST {
    if {[string tolower "[HTTP::host][HTTP::uri]"] starts_with "site.domain.com/urgentalerts/"} {
        HTTP::respond 302 Location "[string map -nocase {"site.domain.com/UrgentAlerts/" "https://site2.domain.com/sites/EmployeePortal/News/_layouts/EmployeePortalMain/go.aspx?C="} "[HTTP::host][HTTP::uri]"]"
    }
}