Resolve domain alias

src/freedombone-base-email

@@ -1042,6 +1042,35 @@ function email_smtp_proxy_through_isp {
         if [ ! "$isp_smtp_password" ]; then
             return
         fi
+
+        temp_proxy_file=/tmp/emailproxy.txt
+        host "$isp_smtp_domain" > $temp_proxy_file
+        if [ -f $temp_proxy_file ]; then
+            temp_proxy_file_lines=$(wc -l < "$temp_proxy_file")
+            # shellcheck disable=SC2086
+            if [ $temp_proxy_file_lines -ge 2 ]; then
+                alias_str=$'alias'
+                if grep -q "$alias_str" $temp_proxy_file; then
+                    # shellcheck disable=SC2002
+                    line_str=$(cat "$temp_proxy_file" | awk 'NF>1{print $NF}' | grep "$alias_str")
+                    if [ ${#line_str} -gt 4 ]; then
+                        #shellcheck disable=SC2116
+                        last_char=$(echo "${line_str:$i:1}")
+                        if [[ "$last_char" == '.' ]]; then
+                            # remove the last character
+                            #shellcheck disable=SC2116
+                            line_str2=$(echo ${line_str::-1})
+                            line_str="$line_str2"
+                        fi
+                        if [[ "$line_str" == *'.'* ]]; then
+                            isp_smtp_domain="$line_str"
+                        fi
+                    fi
+                fi
+            fi
+            rm $temp_proxy_file
+        fi
+
         { echo '# password file used when the local exim is authenticating to a remote';
           echo '# host as a client.';
           echo '#';