AWS Cognito Email customization

I would like to customize invitation email body with emoji but i got an error :

Member must satisfy regular expression pattern: [\p{L}\p{M}\p{S}\p{N}\p{P}\s*]*\{####\}[\p{L}\p{M}\p{S}\p{N}\p{P}\s*]*

I was able to solve this for email header using base64 encoding following this documentationhttps://docs.aws.amazon.com/ses/latest/dg/send-email-raw.html#send-email-mime-encoding-headers, but how am i supposed to do with the body?

Thank you in advance.

Clément