An error occurred while sending mail

I send mail with ThunderBird to Gmail and yahoo, It’s OK!

but when I send to some enterprise email server. this error display!

An error occurred while sending mail. The mail server responded: 5.7.1 <>: Relay access denied. Please check the message recipient and try again.@

how to config it?


For the mail server must be registered DNS record, for example
If no DNS entry for your mail server then other mail servers it is a spam server.
Read more about the MX DNS, and A DNS records.
Check with the command