Bounced messages are messages which are deemed by an E-Mail server as undeliverable. Sometimes this will happen as soon as the server receives the message. There are a few things you can do to check to ensure reliable delivery of your E-Mail messages.

Obtaining Headers or Bounce Back Information:

You should look at the headers or blocked mail information which is included in the message that is sent back to you notifying you of a failure in delivery. These messages will include the reasons why the delivery failed and the original message that was sent. This may help you locate and possibly fix the problem.

If the message was sent by a visitor or user of a forum, content management system, blog or other script running on your CGI server, you will want to ask that the person sending the message send you the full bounced E-Mail message including all headers.

If you are unable to retrieve the bounced mail information, you need to contact the ISP or company that runs the server that the messages are being refused from. You can find the contact information on the provider's web site.

Correct Spelling:

Be sure you have typed in the recipient's E-Mail address correctly. A mistake in the username, placement of dots, or domain name (ie. .net, .com, etc.) can often cause bounced E-Mail messages. Be sure that you have typed in your E-Mail address correctly in any scripts that will be sending you E-Mail.

Use Valid E-Mail Address:

Be sure that the recipient's E-Mail address is valid. It is best never to send E-Mail to people you do not know. If you are using a script, be sure that E-Mail validation is included as part of the script and turned on. Forum scripts may include an option which would send an E-Mail to the newly registered user asking them to validate their E-Mail address by clicking a link in the E-Mail the script sends them before they can post or join the forum. Often this setting is turned off by default and needs to be turned on in the script's configuration settings or administration page.

Use Valid E-Mail Headers:

Usually, if you are sending E-Mail using a major E-Mail program or your domain's web mail, you should not need to worry about E-Mail headers. However, if you are using a script or writing one, be sure the script will send E-Mail messages with valid headers, including a Reply To E-Mail address.

Usage of Spam Keywords, Phrases, or Blocked Domain Names:

You may have triggered a bounced mail message if you had used a keyword, phrase or possibly a blocked domain name in any part of your e-mail message or it's headers. Some servers or even the recipient's mail software may have thought your mail was spam and either sent it to a Spam folder, otherwise marked it as spam, or even deleted the message altogether.

Server Downtime:

It may be that the mail server is down or not functioning properly at that moment. If that is the case, try again later.

Recipient's Mailbox Is Full:

Sometimes, the recipient's mailbox is full and therefore can no longer hold any more messages. They may have used up their quota of space on the mail server due to too many incoming E-Mail messages. In this case, you may want to resend your E-Mail at a later date or look for an alternate E-Mail address to send to.

Is Your Domain or IP Blocked?

It may be that your domain name or IP address has been blocked or blacklisted for some reason from the recipient's mail server. You will need to contact the ISP or administrators of the server which refused the message. Below are a few common servers we have heard had problems. Keep in mind that these servers do not always refuse E-Mail automatically. This list is for your convenience in case you should have problems. Please let us know of any other servers that you have problems with. Always try to contact the server administrators or company owning the server first to get further instructions on how to unblock your domain or IP address.

• Yahoo! Please see their FAQs My E-Mail is being blocked by Yahoo! Mail. What can I do? and As a sender, how can I ensure uninterrupted SMTP access and prioritized delivery?

• AOL: Call AOL's US Postmaster at (703) 265-4670 and have the bounce back information or bounced message available. The process could take between 30 - 45 minutes to unblock your domain or IP from their receiving mail servers.

• Comcast: Send E-Mail to blacklist_comcastnet@cable.comcast.com and include only this IP address in the message body: 24.120.30.5
  
  If the bounced mail was from one of your scripts on your CGI server, you will need to send the IP address of the CGI server instead. Please contact us for more information if you should need your CGI server's IP address if you cannot locate it in the bounced E-Mail message's headers.