Problema enviar email "Mail delivery System"

[netweb]

Estoy intentado enviar un correo y este robota con este mensaje en hotmail:

This is the Postfix program at host smtp-01.piensasolutions.com.

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 Postfix program

<[email protected]>: host
slcc314.piensasolutions.com[217.76.150.228] said: 452 4.2.2 Over quota (in
reply to RCPT TO command)


--Archivo adjunto de mensaje reenviado--
From: [email protected]
To: [email protected]
Subject: xxxxxxxxxxx
Date: Sun, 14 Nov 2010 14:50:40 +0100

y en gmail:

his is the Postfix program at host smtp-01.piensasolutions.com.

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 Postfix program

<[email protected]>: host
slcc314.piensasolutions.com[217.76.150.228] said: 452 4.2.2 Over quota (in
reply to RCPT TO command)

Final-Recipient: rfc822; [email protected]
Action: failed
Status: 4.0.0
Diagnostic-Code: X-Postfix; host slcc314.piensasolutions.com[217.76.150.228]
said: 452 4.2.2 Over quota (in reply to RCPT TO command)


---------- Mensaje reenviado ----------
From: xxxxxxxxxxx <[email protected]>
To: [email protected]
Date: Mon, 15 Nov 2010 00:15:45 +0100
Subject: xxxxxxxxxx

Lo he probado con hotmail y Gmail y no lo consigo. ¿a que se debe?