Caracter Policy messages in html format

Since two days, a problem appears on recepted messages in html format: The caracter policy is blocked as big, and it’s impossible to parameter it .
I have choiced to txt format, and caracter policy is as i have parametered on software.
It is same problem with sended messages in html.
What can i do to resolve it, please?

Christophe T .

Sorry, i have found the problem.
It was the zoom action with fingers on message who is memorized to all html messages when the user did it on the only message.

@ Christophe T.