Puntuado con 5 de 5 estrellas

MailMerge is improving each time ! However, since last time I used it with personnalized attachments, I moved to MacOS. I can't find the way to give the right path to the files and have it attached to the mails generated

Esta valoración es de una versión anterior del complemento (9.1.0). 

You must select the files manually in the field "Attachments -> File" in the Mail Merge Dialog. Then specify the filename in the field "Attachments -> Attachments". See:
https://addons.thunderbird.net/thunderbird/addon/mail-merge/versions/9.0.0