Temporary lookup failure

Without any explanation, now whenever I want to send an email, here is the message I get:

Code:

Mr.XXXXX ([email protected]) le 29/10/2013 10:41

            Erreur serveur : '451 4.3.0 <[email protected]>: Temporary lookup failure'

Unable to send an email using the IMAP server service. Any idea?

Thank you

 

Thank you for your reply.

I see this:

For me, all is ok...