después de buscar un poco por ahí:(en inglés lo siento)
This issue comes down to SMTP server permission. The SMTP classes work quite well if you attempt to hit an SMTP server that will accept your message. The error message that you posted indicates that you are trying to send mail thru a server that doesn't want you to send mail thru it.
For most mail servers you can successfully send a message thru it if you meet one of several conditions:
1) You are sending mail to an address that the server recognizes (i.e. you talk to mail.mydomain.com and tell it you have a message for [email protected]. The server handles the mailbox for me@ and accepts a message for it.)
2) You are sending a message thru an SMTP server to which you have already authenticated. This is how many email programs can send messages. You connect to your mailbox server and authentication with a mailbox (POP) login. The server recognizes traffic from your computer as legitimate because you logged in successfully within some time period.
3) You are sending a message from a computer with a permitted IP address. This could be either a public IP that the server knows about or an internal address (LAN). Most corporate email systems and broadband networks are set up this way. They'll accept mail from a LAN address (or public IP address that is within its realm of control) because it is assumed to be legitimate, but other connections are filtered out based on other criteria.
4) (Not 100% sure on this one). You ([email protected]) send a message to someone else ([email protected]) thru the mail server that should recognize you as a legitimate address (mail.yourdomain.com). If the server can validate your address as legitimate it will accept the message to me.
These are the conditions I am familiar with. If you don't meet one of these, the server will reject your message because it is regarded as mail relay. Typically mail servers are not set up to accept mail relay because it promotes SPAM. It looks like you are falling victim to condition #4.
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