diff --git a/zabbixinstall b/zabbixinstall
index 6797daa..3254108 100755
--- a/zabbixinstall
+++ b/zabbixinstall
@@ -67,30 +67,11 @@ usage() {
     printf -- "  -h | -help | --help   Show this help screen\n\n"
 }
 
-#
-# Function inputcheck
-#
-inputcheck () {
-    [[ -z "$hostname" ]] && { usage; echo "ERROR: DOMAIN CANNOT BE EMPTY!"; exit 1; }
-    [[ "$hostname" =~ [[:space:]/] ]] && { echo "ERROR: DOMAIN INVALID (no spaces or slashes allowed)"; exit 1; }
-    [[ -z "$dbpass" ]] && { usage; echo "ERROR: DATABASE PASSWORD CANNOT BE EMPTY!"; exit 1; }
-}
-
 #
 # Let's go
 #
 clear
 
-#
-# Try to determine the latest Zabbix version
-#
-zabbix_version=$(curl -s https://repo.zabbix.com/zabbix/ | grep -oP '(?<=href=")[0-9]+\.[0]' | sort -V | tail -1)
-
-# Use fallback version if fetch failed
-if [[ -z "$zabbix_version" ]]; then printf "Could not determine latest Zabbix version. Falling back to version %s\n\n" "$fallbackversion" ; zabbix_version="$fallbackversion" ; fi
-
-printf "Using Zabbix version: %s\n\n" "$zabbix_version"
-
 #
 # Configure command line options
 #
@@ -108,7 +89,54 @@ while getopts ":n:p:m:a:h" option; do
         \?) usage; echo ""; echo "Error! Invalid option: -$OPTARG"; echo ""; exit 1;;
     esac
 done
-inputcheck "$hostname" "$dbpass"
+
+#
+# Validate hostname and DB password
+#
+if [[ -z "$hostname" || -z "$dbpass" ]]; then
+    usage
+    printf "\nERROR: Both -n (domain) and -p (database password) are required.\n\n"
+    exit 1
+fi
+
+# Convert to lowercase (domains are case-insensitive)
+hostname=$(echo "$hostname" | tr '[:upper:]' '[:lower:]')
+
+# Disallow leading hyphen
+if [[ "$hostname" =~ ^- ]]; then
+    printf "\nERROR: Domain cannot start with a hyphen.\n"
+    printf "Example of valid input: zabbix.example.com\n\n"
+    exit 1
+fi
+
+# Disallow spaces, slashes, underscores
+if [[ "$hostname" =~ [[:space:]/_] ]]; then
+    printf "\nERROR: Domain cannot contain spaces, slashes, or underscores.\n\n"
+    exit 1
+fi
+
+# RFC 1123 validation
+if [[ ! "$hostname" =~ ^([a-z0-9]+(-[a-z0-9]+)*\.)+[a-z]{2,}$ ]]; then
+    printf "\nERROR: Invalid domain format.\n"
+    printf "Example of valid input: zabbix.example.com\n\n"
+    exit 1
+fi
+
+# DB password sanity check
+if [[ "$dbpass" =~ [[:space:]] ]]; then
+    printf "\nERROR: Database password cannot contain spaces.\n\n"
+    exit 1
+fi
+
+#
+# Try to determine the latest Zabbix version
+#
+zabbix_version=$(curl -s https://repo.zabbix.com/zabbix/ | grep -oP '(?<=href=")[0-9]+\.[0]' | sort -V | tail -1)
+
+# Use fallback version if fetch failed
+if [[ -z "$zabbix_version" ]]; then printf "Could not determine latest Zabbix version. Falling back to version %s\n\n" "$fallbackversion" ; zabbix_version="$fallbackversion" ; fi
+
+printf "Using Zabbix version: %s\n\n" "$zabbix_version"
 
 #
 # Download and install the Zabbix repository