How to fix "Error in processing. The server response was: Greylisted, please try again in X seconds"

Yes! A solution for this strange error! How many times have you seen this one while trying to send an e-mail?

I had a quite interesting Friday. It was the last day of a class in which I had to replace the trainer. They had some problems with him and I was the choosen one for the replacement. Everything went well so far. After that I went to check the error log of my blog (I use Elmah, by the way) and I found an issue I've never seen before:

System.Net.Mail.SmtpException
Error in processing. The server response was: Greylisted, please try again in 240 seconds

The time may vary. But after google it for a while I found it! My server was implementing Greylisting which, according to Wikipedia, is a method of defending e-mail users against spam. So, the non-recognized e-mails are automatically rejected for a while.

And how to fix that?

All I needed to do was to create a mail account on my server and add it to my web.config in the following way:

<system.net>
	<mailSettings>
		<smtp>
			<network defaultCredentials="false" host="Mail@DomainName.com" port="25" userName="username@DomainName.com" password="ThisIsAPassword"/>
		</smtp>
	</mailSettings>
</system.net>

Needless to say, you need to put your own host, username and password. :-)

And that's it.

In time: The answer I found here.

	<system.net>
		<mailSettings>
			<smtp>
				<network defaultCredentials="false" host="mail.davidsonsousa.net" port="25" userName="contact@davidsonsousa.net" password="D#sousa12"/>
			</smtp>
		</mailSettings>
	</system.net>