[imp] mail is returned

[kintango at tiscali.es]

Hello.
I have a problem sending mail to more than one recipient.

The mail is sended to all recipients, but allways, the sender receive a
returned mail from the smtp server.

smtp server: Microsoft exchange 5.5
imp 3.1
php 4.3.2
c-client 2002d
debian potato

Maybe the problem is with the commas in the address.

message from smtp server:
________________________________
This is the Postfix program at host mailserver.com.

I'm sorry to have to inform you that the message returned
below could not be delivered to one or more destinations.

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 message returned below.

                        The Postfix program

<user1 at server.com>: user unknown. Command output: : Mailbox does not exist
_
    

<user2 at server.com>: user unknown. Command output: : Mailbox does not exist
_



------------------------------
Tiscali ADSL Libre 
http://adsl.tiscali.es/index.php3?produc=libre&did=&despl=&did=adl-7380017

¡¡¡VELOCIDAD 24h. DESDE SÓLO 16,95 €/mes + TIEMPO DE CONEXIÓN!!!
Con las mismas prestaciones que una línea ADSL estándar
------------------------------