Valid FROM 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 with very little validation, Best Practices documents describe the need to give enough information that will help the recipient and email server operators to identify who is sending the information.

In order to ensure that messages are not stopped by this check, the sending server or email client software has to make sure that the FROM: address that is sent conforms to some very simple rules.

The FROM string received should in the style of:



The following bad examples will get rejected:


As well, the FROM address is important as it is the address that would be used if problems were encountered delivering the message, so if the address can’t be responded to, we should not accept the email from that address either. So the domain portion of the email address provided will need:

a) An A record that DNS can resolve, which will show where to respond..
— or —
b) An MX record that DNS can resolve, which will show where to respond.

If both are missing, we should reject the email as we cannot respond properly if there is a problem. Spammers will often try to forge this information, but it is a lot harder for them if they are required to use valid domains, and they usually have little control over the DNS, especially if they are using trojans, bots or compromised machines. 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 is NOT the From: information that you type in your email, (ie in the section where your email client shows To:, From: and Subject:) but this is normally what you use as login information or setup information for your email account.

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

Normally when you send email through an outgoing email server you have to login with user name and password. These are your outgoing email server settings. Sometimes you don’t fill that information in, and that means that your outgoing email server does some of this for you. If you have to set up SMTP or Outgoing Email Server information in your email client, you will either use your email name, or a user if assigned to you by your ISP. If you are using just the ‘user’ information assigned by your ISP, often the ISP mail server will add ‘’ to the end of your user and use that for the FROM information it uses when contacting other mail servers. If you need to provide your email information for logging into the outbound server, it will use that. Sometimes some ISP’s let their customers use anything, and in that case your email client normally is smart enough to use your email address as the FROM. But if you setup your email client with junk information or the incorrect information in the outbound email settings, you can run into this problem, and get your email blocked.

Normally, this rule will only block spammers who try to forge information to hide their identity. If you get this message, the best thing to do is to call your ISP support line for help on setting up your email client. If you are the intended recipient, this is something you can’t do any thing about. The sender will have to fix their settings, even if they can send to others and not you.