Should you know who is sending you emails? Like Caller ID on your phone, it's important to know who is actually trying to contact you. With a phone, we can decide to pickup or not. We can even set up the phone to reject any calls from callers blocking their number.Email should be the same way, but we don't have as much control over what gets accepted in our mailbox. Every minute, junkmail comes flying towards our mailboxes. If you have Spam Filters, the junk might be getting caught at the server level, or it may get downloaded in your email client (like Outlook) and then get filtered and sorted.
But, what if we could stop some of them before they even get close to the filters? Doing so would be saving the resources of the server doing the filtering, and your own computer, and your poor troubled eyes wading thru the junk. That's what a 'Sender Verify' is for on the Mail Server.
Many mailservers are now implementing Sender Verify on their systems. Sender Verify has been an accepted standard for a long time, but was not always implemented in the past. A lot of 'standards' haven't been enforced for a long period of time, and this is because a lot of servers were misconfigured. Enforcing the 'rules' would cause havoc for a lot of users, and ISPs and Server Administrators did not want to upset customers with blocked emails. But as more and more users complain about spam, the focus is now leaning towards finally enforcing the standards.
Sender Verify is quite simple. The receiving mailserver checks to see who sent the email, and verifies that the address is valid. It can do this by checking to see that the domain name is valid, and check to see if the 'sender' is accepting emails at that address. Here is an example of a server checking incoming mail.
2007-02-07 04:53:37 H=(localhost.localdomain) [188.8.131.52] F=
Edit 2008-July: It looks like the example got truncated when transferring to the new site.
This is just a 4 hour sampling, showing JUST rejected email to ONE email address. 28 emails, blocked from even entering the server for a chance to get around the filters. 28 in 4 hours. In about 12 hours, that would be just under 100 emails blocked.
Sometimes, legitimate email gets blocked. Why? Because the sending server is misconfigured. Misconfigured might be too strong a word. Perhaps it's configured the way it has always been for the last 10 years and has always worked fine. Problem is, it's time for the server to get in line, to change with the times. The accepted standards have been in place for a long time, and they are finally, slowly, being enforced.
It won't stop spam, but it might slow it down just a little bit.