January 17, 2012

Blocking Senders

E-mail is a great tool for communication but there are times when one does not want to receive any messages from certain senders. There are many potential reasons for this: personal, relational, legal. But the bottom line is that you no longer want to receive messages from this sender in your Inbox.


Blocking a Sender

Some e-mail providers have a system to block or blacklist specific senders. In most cases it's simply an easy-to-use front-end to a filter system: you provide an e-mail address and it builds a filter for you to auto-delete any messages from that sender. The exact same form of blocking is available in Gmail* except that you explicitly create the filter, which of course allows you more control over how it works and what it does with the messages. The down-side is it take more effort than just entering an e-mail address in some field.

Typically you will simply want to delete the messages. But there may be a case where there is some personal or legal reason you need to save these "blocked" messages. In such a situation you might label the messages, archive them (so they are not in the Inbox), and mark them as read. This is an example of why having full control over the filter is important.

So to create a simple blocking filter, do the following:
  1. Go to Settings->Filters
  2. Click the "Create a new filter" link towards the bottom of the page.
  3. Enter the sender's e-mail address in the From field
  4. Click the "Create filter with this search" link.
  5. Check the box for "Delete it".
  6. [optional] Check the box for "Mark as read".
Gmail help article: http://support.google.com/mail/bin/answer.py?hl=en&answer=8151

It may be interesting to note that Google Apps accounts do have the ability to do blocking: http://support.google.com/postini/bin/answer.py?hl=en&answer=141187 although this can only be done by the domain administrator.


Blocking with a Return Error Message

While the above process will satisfy most blocking requirements, there are times when one may want the sender to know their message was not delivered. That is, you want them to receive a bounced error message.

While there are a few providers that have this capability, it is not something Gmail supports. Even so, it is possible to simulate, or fake a bounced message back to the sender. Just like the above blocking, it involves creating a filter, but it adds the use of the Canned Response capability (Settings->Labs->Canned Response). So with the Canned Response lab enabled:
  1. Compose a message.
  2. Use the "Canned Responses" drop-down menu and select "New canned response..."
  3. Give it a name.
  4. Complete the message content (see below) and save the draft.
Now what should the canned response say? It needs to look similar to a real bounced message. Even so, it's not going to look exactly like one since it is being simulated. I would suggest something similar to the following which is the proper format and contains a correct SMTP error code for a refused message.
Delivery to the following recipient failed permanently:
your.name@gmail.com
Technical details of permanent failure:
The requested recipient could not be reached.
You do not have permission to send to this recipient.
SMTP Error 550 5.7.1 Requested action not taken: message refused.
Note: you should fill in your correct e-mail address in place of "your.name@gmail.com" to match the correct failure format. There's no problem using your address since they already have the address in order to send the message in the first place. It's not any new information. But if one is really concerned (paranoid) you could replace it with something like "*****@gmail.com" as if the address had been masked out. It just will look that much less like a true bounced message.

An alternative message that's a bit more to-the point about why it failed:
Delivery to the following recipient failed permanently:
your.name@gmail.com
Technical details of permanent failure:
SMTP Error 550 5.7.1 Rejected, your address is blacklisted by the recipient.
Unlike the earlier message that has some ambiguity, this one clearly says the sender was blacklisted.

Alternatively, you could use the error for a non-existent account which might suggest you deleted it:
Delivery to the following recipient failed permanently:
your.name@gmail.com
Technical details of permanent failure:
Google tried to deliver your message, but it was rejected by the recipient domain. We recommend contacting the other email provider for further information about the cause of this error. The error that the other server returned was: 550 550-5.1.1 The email account that you tried to reach does not exist. Please try
550-5.1.1 double-checking the recipient's email address for typos or
550-5.1.1 unnecessary spaces. Learn more at
550 5.1.1 http://support.google.com/mail/bin/answer.py?answer=6596 im3si6082088bkc.81 (state 13).

And now create the actual filter:
  1. Go to Settings->Filters
  2. Click the "Create a new filter" link towards the bottom of the page.
  3. Enter the sender's e-mail address in the From field
  4. Click the "Create filter with this search" link.
  5. [optimal] Check the box for "Skip the Inbox (Archive it)"
  6. [optinal] Check the box for "Apply the label" and select one from the drop-down list.
  7. Check the box for "Send canned response" and select one from the drop-down list.
  8. [optional] Check the box for "Mark as read".
Note 1, and this is important, you can not check the box to delete the message because the system will not send a canned response for a deleted message.

Note 2, the optional steps are basically to keep these messages out of your Inbox by placing them in a label of your choice. You can then decide to save them if needed, or every so often go and delete all the messages in that label.

Clearly this system isn't perfect. The biggest problem being that you can't delete the message and also send the canned response. Still, it's a reasonable work-around given that Gmail doesn't have the ability to bounce a messages. And it will satisfy the needs some users have to block a sender with a message so they know they are blocked.

Of course, as already mentioned, it may not fool a more knowledgeable e-mail user. But what can they do about it? If they send a message saying "I know it's fake" all they'll get is another failure report.

Summary

It's unfortunate that there are reasons why one may want or need to block a sender from e-mailing to your account. But fortunately Gmail provides the tools to keep such messages out of your Inbox. It may take some self-control to not look at them in Trash if the content may be disturbing. But they can be deleted permanently without opening.

And the workaround for simulating a bounced error return is pretty easy to setup and use. It should work for most cases, and help provide one a level of protection from unwanted contact.





* Gmail is a trademark of Google, Inc. This page is not sponsored by or affiliated with Google.