SMTP E-mail error messages

Q. When trying to email a confirmation this is the message: "Couldn't send message!  Response:553 sorry, that domain isn't allowed to be relayed thru this MTA (#5.7.1)".  How do I fix that?

(This relates to any similar error response.)

The error is coming from the SMTP server that you're sending mail through, so it's likely to be the Sender address you're using.  If you're not a recognized sender for the SMTP server you're using, it may not allow relaying the message.  This is to keep spammers from using it from the outside.  Especially if it allows sending a test message to yourself (because you're recognized) but not to others, this is likely the problem.

For instance, if you're using an SMTP server from your web provider like "smtp.myparkaddress.com", your Sender E-mail address should be a valid address for your domain, like "info@myparkaddress.com".  Likewise, to use an ISP's SMTP server like "mail.earthlink.net" you may have to use your earthlink.net E-mail address for the Sender address.