It seems that there is a bug in MBM. In French, there are some typographical rules to the effect that some letters must be linked, eg œ, æ, etc.
MBM has this behavior: in the message window, the ligatures are correct, but in the preview window, and also in the sent message, they are not.
Please correct.
Regards,

Gérald

Have you tried to use the ISO-8859-15 encoding rather than ISO-8859-1? The encoding setting for the current document can be changed from the 'Message' panel, below the 'Format' pulldown menu and for all future documents from the MaxBulk Mailer preferences.