What does "550 550 5.4.1 Relay Access Denied (state 14)." mean?

I am getting this message when I send an email to a corporate email address from my google-apps account:

Google tried to deliver your message, but it was rejected by the recipient domain. We recommend contacting the other email provider for further information about the cause of this error. The error that the other server returned was: 550 550 5.4.1 Relay Access Denied (state 14).

Maybe it just means the address is bad, but if I try a definite bad email I get:

Google tried to deliver your message, but it was rejected by the recipient domain. We recommend contacting the other email provider for further information about the cause of this error. The error that the other server returned was: 550 550 5.4.1 @.com: Recipient address rejected: Access Denied (state 14).

Can anyone suggest why the slightly different responses?

Solution 1:

550 Relay Access Denied is often a catch-all response for when mail is rejected, commonly due to falling into a spam filter.

Reasons could include actual spam detection (bulk mailing, or perhaps an overzealous spam filter setting), or a misconfiguration on your Google Apps domain settings where your domain's MX records don't match what IP the server is connecting from (seems unlikely).

I would definitely mention it to the mail administrator of your corporation. You may have uncovered a configuration issue that is also preventing a bunch of other people's email from arriving properly, possibly losing your company business.

Solution 2:

I can see the thread is quite old, but a simple Google search sent me here, so I hope it can help other people.

I saw this error message today (a mail sent from a gmail address to an office 365 enterprise address).

The error was just the person tried to send the mail to [email protected] instead of [email protected] :)

So, if you get this message, you can double-check the recipient's address you typed.

PS: sorry if my English is basic, I'm a French user!