Occassionally one of your emails is bounced back to you with a bounce message that looks something like this...
From: Mail Delivery Subsystem [mailto:MAILER-DAEMON@mail03.syd.optusnet.com.au] Sent: Friday, 10 March 2012 1:05 PM To: email@example.com Subject: Returned mail: see transcript for details The original message was received at Fri, 10 mar 2012 13:05:15 +1000 from a19-123-45-67.sbr802.nsw.optusnet.com.au [184.108.40.206] ----- The following addresses had permanent fatal errors ----- (reason: 550 5.7.1 Recipient not authorized, your IP has been found on a block list) ----- Transcript of session follows ----- ... while talking to mail.receiversdomain.com.au.: DATA <<< 550 5.7.1 Recipient not authorized, your IP has been found on a block list 550 5.1.1 ... User unknown <<< 503 5.5.2 Need rcpt command
All of the information to resolve the issue is generally included in the bounce message. There are a number of different codes, which are explaned below, but generally most bounce messages include the reason for the bounce in the message.
There are three important pieces of information in a bounce message;
1. What server your message was sent through.
The message above was sent from your computer through your internet connection using your ISP's mail server. In the example above the sender is using Optus for their internet. This information is highlighted in blue above.
2. The IP address provided by your ISP
This is generally right after the server info. In the example above, your IP address is highlighted in red.
3. The reason for the bounce
In the example above, the reason for the bounce is highlighted in brown. The message was bounced back because the sending IP address (your IP address) highlighted in red was found on a block list. Block lists exist to help email providers reduce the burden of spam, and to stop obvious spam arriving in their customers' mailboxes. In some cases however, you can be unlucky enough to get an IP address from your internet provider that another person has used to send spam. The best way to deal with this is described below.
What to do if you've ended up on a block list
If you've ended up on a block list, it's likely that some of you mail messages are getting bounced back to you. The best way to deal with this is to follow the instructions below. You should hopefully be back up and running in just a few minutes.
Go to http://clients.domainhostingshop.com.au/what-is-my-ip/ where you can find out what your IP address is. Make a note of it, as you'll need to know this in Step 3.
Reboot your modem. Generally you just need to switch it off, wait a minute or two, and switch it back on again. If you're using a USB 3G modem, unplug the modem and wait a minute or two and then plug it back in again.
When your internet connection is back on, go to http://clients.domainhostingshop.com.au/what-is-my-ip/ again, and see what your IP address is again. If it's different, you should be able to send mail again without any problems. If it's the same, you'll probably need to contact your internet provider to report the issue. They'll need to know what your IP address is, and liuckily you've written it down from step one.