Problème d'envoi d'e-mail!!! aidez moi svp

Bonjour, hier j'ai essayé d'envoyer un mail mais on m'a renvoyer un message me disant ça avec outlook

This is the mail system at host mwinf2a10.orange.fr.

I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

The mail system

<....@hotmail.com>: host mx2.hotmail.com[65.54.244.168] said: 550
Requested action not taken: mailbox unavailable (in reply to RCPT TO
command)

et ça avec orange:

Un message a ete emis depuis votre compte de messagerie.

Certains destinataires n'ont pas recu votre message.
Vous trouverez en piece jointe le message qui n'a pu etre delivre.
Nous vous invitons a verifier l'adresse des destinataires et a essayer
de renvoyer le message.



This is the SMTP Server program at host orange.fr.

I'm sorry to have to inform you that your message could not be
be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to <postmaster>

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

The SMTP Server program



<...@hotmail.com>: host mx3.hotmail.com[65.54.245.72] said: 550
Requested action not taken: mailbox unavailable (in reply to RCPT TO
command)

C'est quelquechose d'important donc merci de me répondre au plus vite, je ne sais plus quoi faire!!!