Symptoms

When including Cyrillic symbols after </style> tag in WEB-INF\classes\templates\email\html\includes\header.vm and save the file in UTF-8, you still received email notification with garbled symbols instead of correctly encoded Cyrillic characters.

Resolution

1. Fill in the Cyrillic characters into Mixed input field in this website: http://www.rishida.net/tools/conversion/ and click on Convert
2. Copy the converted results of Hexadecimal NCRs or Decimal NCRs and paste it after </style> tag
3. Save header.vm
4. Restart JIRA