Use the {{PLACEHOLDER}} syntax in the subject or body. The placeholder name must match a mapping key above (case-insensitive, whitespace-tolerant).
Example: mapping key FIRST_NAME → write Hello {{FIRST_NAME}}, in the body.
All of these forms are accepted and resolve to the same mapping:
{{FIRST_NAME}} — standard uppercase
{{ SPECIALTY }} — extra whitespace inside the braces is ignored
{{first_name}} — lowercase (case-insensitive match)
Every placeholder used in the subject or body must have a corresponding entry in Dynamic Mappings above — unmapped tokens will be left as-is.