Block IP in Address

Information Details

Normally, the reason you have reached this page is because a mail server has sent you a message when it rejected an email from you, or one of your users.

  • If you are an email or network operator, you can continue reading this section
  • If you are a user sending email and it got blocked, you should read this section instead

Information for Email and Network Operators

Although email servers can by RFC accept connections that are addressed to ‘john@’, most email servers and anti-spam tools will not expect or allow this behaviour. Whether it is the sending address or the recipient address. This practice does not supply enough information to safely route email. This is a simple rule which just insists that the format be NOT @ip_address.

In order to ensure that messages are not stopped by this check, make sure the FULL email address of the recipient AND the sendor is used.

The RCPT TO: string received should in the style of:



The following bad example(s) will get rejected:


Spammers will often try to send email to just ‘john@ip_address’ hoping that user exists on a system. It is a lot harder for them if they are required to use valid domains. If you are the one sending the message, and you were blocked with this message, it is most likely that you do not have your email client set up correctly, and you should read the next section.

Information for users. Why was my email blocked?

If your email was blocked, and the link sent you here it is probably because your email client is not set up correctly, or your outgoing mail server is setup incorrectly. This may NOT be the From: information that you type in your email, (ie in the section where your email client shows To:, From: and Subject:) but also may be part of what your specified when you entered in your account settings.

The main problem will usually be in your email/account settings, (eg. in OutLook or Thunderbird)

Carefully check the To: and From: addresses in your sent folder and you will usually see the simple mistake. Make sure you use the FULL email address. If you don’t see the mistake there, then it may be in your account settings instead. Sometimes this rule can get triggered if you include strange characters in your to address, that your outgoing mail server did not know how to parse correctly, and your outgoing mail server isn’t set up according to Best Practises.

Normally, this rule will only block spammers who try to send blanket email blasts to common names hoping that the recipient exists on the destination server. Please check the email address that you tried to send to, and once you fix that you can try again. Or to try to get the sender address past some anti-spam tools.