@kanhu sorry for the delay… It’s not that simple, sometimes we send a mail to quite a lot of contacts to send news (about 50 to 100 persons), so we can’t call them one after one to know who receive or not… And it seems like some of them don’t receive. And my brother stopped using the mail of my server because it was often considered as spam.
Now I have another problem : Virus qui envoie des mails en masse (spam), so maybe it’s linked…