Error sending messages

[luis.bances]

hello all, somebody could help me solve the following problem, I connect from my house to my mail from my outlook resibir mails can smoothly but I can not send a user who is not my domain I get the following error:
From System Manager
Sent: Wednesday, 07 January 2009 12:50 p.m.
To: chapa@pragmaddb.com.pe
Subject: No surrender: saludos
Some of the recipients have not received your message.
Subject: RV: saludos
Posted on: 07/01/2009 12:50 PM
Unable to locate the following recipients:
'luis.bances @ gmail.com' on 07/01/2009 12:50 PM
501 5.1.3 Bad recipient address syntax
someone can help me
thanks

[Bill Brock]

It looks like you may have blank spaces in the e-mail address.