Zabbix

........S. [ZBXNEXT-10244] updated email header generation by adding Message-ID field and updating In-Reply-To field

Merge in ZBX/zabbix from feature/ZBXNEXT-10244-7.5 to master

* commit 'dfc3b1f141e722f683e2a606f0145e2ab7a3385e':
  ........S. [ZBXNEXT-10244] cleaned up SQL query
  ........S. [ZBXNEXT-10244] added missing comments and other minor fixes
  .......... [ZBXNEXT-10244] removed unused variable
  ........S. [ZBXNEXT-10244] fixed e-mail Message-ID generation
  ........S. [ZBXNEXT-10244] moved alert macros to zbxalerter.h
  ........S. [ZBXNEXT-10244] minor refactoring
  ........S. [ZBXNEXT-10244] removed redundant code
  ........S. [ZBXNEXT-10244] fixed review comments
  ........S. [ZBXNEXT-10244] added different right side values to Message-ID based on type
  ........S. [ZBXNEXT-10244] updated email header generation by adding Message-ID field and updating In-Reply-To field