[otrs] Special characters in survey emails

Hello OTRS fans, I'm currently implementing the survey module and found an issue: The customer e-mail content stored in the param "Survey::NotificationBody" does not show special character nor accents in the sent e-mail. I did a hard job to have special characters correctly displayed in all parts of OTRS (web interface, e-mails, LDAP) and everything works fine except for survey e-mails. Can anyone help on this please ? Thanks and regards, Régis