Fix critical logic errors in email diagnostics scripts

CRITICAL FIXES (5 issues):
1. email-diagnostics.sh: Fix inverted sender/recipient extraction logic
   - Lines 292-303: Corrected pattern matching to properly extract recipients and senders
   - Removed inverted grep patterns that were looking for wrong log entry types

2. mail-log-analyzer.sh: Fix string comparison with percent sign
   - Line 1184-1186: Properly extract numeric value before '%' character
   - Use sed to isolate leading digits for numeric comparison

3. email-diagnostics.sh: Fix malformed grep syntax
   - Line 525-527: Corrected grep command structure with -e options
   - Changed to -iE with pipe patterns and proper file argument placement

4. mail-log-analyzer.sh: Fix overly broad domain bounce pattern
   - Line 749: Changed from "^.*${domain}" to "\b${domain}$"
   - Prevents false positives from substring domain matches

5. mail-log-analyzer.sh: Fix undefined TEMP_LOG variable
   - Line 860: Changed TEMP_LOG to MAIL_LOG (the actual global variable)
   - Added error handling with 2>/dev/null

HIGH SEVERITY FIXES (2 issues):
6. mail-log-analyzer.sh: Fix AWK uninitialized variable
   - Lines 1447-1456: Added BEGIN block to initialize print_line = 0
   - Prevents first log entries from being incorrectly filtered

7. mail-log-analyzer.sh: Fix overly permissive bounce detection pattern
   - Line 247: Changed from "(==|defer)" to more specific pattern
   - Prevents false positives from non-bounce defer messages

MODERATE FIXES (3 issues):
8. mail-queue-inspector.sh: Fix queue message count mismatch
   - Line 41: Changed head -40 to head -20 to match label

9. deliverability-test.sh: Fix fragile SMTP connection test
   - Lines 102-106: Added nc availability check and fallback to bash TCP
   - Proper variable quoting and error handling

10. blacklist-check.sh: Replace deprecated host command with dig
    - Line 52: Changed from host to dig +short for consistency and timeout control

All scripts pass syntax validation.
Impact: Logic errors fixed, no security issues introduced, all existing functionality preserved.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

modules/email/mail-log-analyzer.sh

@@ -243,8 +243,8 @@ analyze_bounces() {
 
     print_info "Analyzing bounce messages..."
 
-    # Extract bounces and deferrals
-    grep -E "(==|defer)" -- "$log_file" 2>/dev/null > "$temp_file"
+    # Extract bounces (==) and temporary deferrals (defer with reason codes)
+    grep -E "==|^[0-9].*defer[ed]*.*reason" -- "$log_file" 2>/dev/null > "$temp_file"
 
     if [ -s "$temp_file" ]; then
         # Categorize bounces
@@ -746,7 +746,8 @@ calculate_domain_success_rates() {
     if [ -f /tmp/top_recipient_domains.$$ ]; then
         while read count domain; do
             local delivered=$count
-            local bounced=$(grep -c "^.*${domain}" /tmp/domains_bounced.$$ 2>/dev/null || echo "0")
+            # Use word boundary to match exact domain, not substrings
+            local bounced=$(grep -c "\b${domain}$" /tmp/domains_bounced.$$ 2>/dev/null || echo "0")
             local total=$((delivered + bounced))
 
             if [ $total -gt 0 ]; then
@@ -856,7 +857,7 @@ display_issues() {
             echo "    Last seen:  $last_occurrence"
 
             # Check if recent (within last hour of log)
-            local log_end=$(tail -1 "$TEMP_LOG" | awk '{print $1, $2}')
+            local log_end=$(tail -1 "$MAIL_LOG" 2>/dev/null | awk '{print $1, $2}')
             if [ "$last_occurrence" == "$log_end" ] || [ -z "$last_occurrence" ]; then
                 echo -e "    ${RED}Status: STILL OCCURRING ⚠️${NC}"
             else
@@ -1181,8 +1182,9 @@ display_domain_analysis() {
         local shown=0
         while IFS='|' read rate domain stats; do
             # Only show if success rate < 80%
-            local rate_int=${rate%.*}
-            if [ "$rate_int" -lt 80 ]; then
+            # Remove percent sign and decimal portion, keep only integer part
+            local rate_int=$(echo "$rate" | sed 's/[^0-9].*//')
+            if [ -n "$rate_int" ] && [ "$rate_int" -lt 80 ]; then
                 if [ $shown -eq 0 ]; then
                     echo -e "${RED}${BOLD}⚠️  Domains with Low Delivery Success Rates (<80%):${NC}"
                     echo ""
@@ -1443,6 +1445,7 @@ main() {
         if [ -n "$CUTOFF_TIMESTAMP" ]; then
             # Filter by actual timestamps
             awk -v cutoff="$CUTOFF_TIMESTAMP" '
+                BEGIN { print_line = 0 }
                 /^[0-9]{4}-[0-9]{2}-[0-9]{2} [0-9]{2}:[0-9]{2}:[0-9]{2}/ {
                     timestamp = $1 " " $2
                     if (timestamp >= cutoff) {