email probs

Προσπάθησα να στείλω ένα email χτες, αρχικά απο Gmail.

Μετά απο λίγο μου ήρθε Το εξής failure notice :
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This is an automatically generated Delivery
Status Notification
Delivery to the following recipient failed permanently:

  trainer@oaed.gr

Technical details of permanent failure:
PERM_FAILURE: SMTP Error (state 9): 550 5.7.1 ...
Relaying denied.
Proper authentication required.

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Μαλακία του gmail λέω, ας το στείλω απο yahoo...

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Hi. This is the qmail-send program at yahoo.com.
I'm afraid I wasn't able to deliver your message to
 the following addresses.
This is a permanent error; I've given up.
Sorry it didn't work out.

<trainer@oaed.gr>:
62.103.147.201 does not like recipient.
Remote host said: 550 5.7.1 <trainer@oaed.gr>...
Relaying denied.
Proper authentication required.
Giving up on 62.103.147.201.

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Όταν λέει proper authentication τι σκατά εννοεί?
Μήπως να το στείλω με περιστέρι?