Hosted email security services can do things that you couldn’t or wouldn’t do on a local email server. And since these security features don’t involve local servers, the average enterprise IT team would know nothing about them. Here are four examples:
1. They can deliberately defer email
With hosted email security, you can deliberately defer an incoming email, bouncing it back while neither delivering it nor rejecting it. Deferring is usually done because of technical problems at the receiving end, but in this case it’s done intentionally to weed out spammers.
Deferred email does not disappear—typically, the sending server will automatically retransmit a few minutes later.
2. Deferring email can filter spam
The ability to defer e-mail may not sound like a useful security feature—except that, with hosted email security, you can have the recipient automatically defer all messages from any IP address that the host is not familiar with. A legitimate sender’s SMTP will automatically retransmit the deferred email a few minutes later, and the hosted email security system that’s receiving it can then treat the message in a normal fashion.
Spammers’ software is typically crude stuff, and not carefully crafted to enhance customer satisfaction. It’s written solely to blast out email and can’t do anything else—like handle deferred messages. Consequently, any sender that responds to a deferral by retransmitting is almost certainly legitimate. Classic spam will simply not get past this simple deferral barrier.
Typically, the “barrier” can be adjusted to retest a given IP address at intervals with another deferral, to make sure that the address is still legitimate. Otherwise, once tested, email from a specific address will go through without being deferred.
3. They can use SPF technology
Phishing emails are all the more dangerous because they are not just blasted out, but carefully targeted, typically from spoofed addresses. However, a hosted email security system can use Sender Policy Framework (SPF) technology to spot emails with spoofed addresses and block them before they can do harm. With SPF, the recipient can gauge the legitimacy of a sender before any email from that sender is accepted.
The entries for individual domains within the distributed Domain Name System specify which computers are allowed to send emails for that domain. Thus, a recipient can check to see if the sending computer was authorized by the domain that the message purportedly came from. Those emails that fail the test are blocked. Since spam and phishing emails typically come from anywhere but their stated origins, SPF can be another level of defense.
SPF does require an additional level of processing, making it more suitable for a host-based system.
4. They can use DKIM technology
SPF only looks at a message’s header information. An additional technology, called Domain Keys Identified Mail (DKIM), additionally looks at the contents of the message when deciding if the message is legitimate.
Using a form of cryptographic authentication, DKIM lets a recipient be sure that an email was actually sent from a specified domain. It can also detect if the message was altered during transit.
The sending software adds an DKIM signature field to the message within its markup tags. The field includes a hash of the message—i.e., a value derived from algorithmically processing the message itself. If the recipient can decode the hash using the sender’s public key (available from the Internet) and the contents of the message, the recipient can be assured that the message is from the stated sender—and it was not altered after the hash was calculated.
The creation and examination of the hash obviously requires computational power over and above what’s typically involved in email handling. Consequently, it’s best handled by hosted software, typically within a cloud service that can assign CPUs as needed.
All-in-all, the technologies available with hosted email security offer an enterprise a new world, one devoid of all but the most carefully targeted spam. The frustrations, wasted time, and out-right risks associated with spam and phishing can become a thing of the past using hosted solutions that can be provisioned in an afternoon.
Ask for a Sendio hosted email security demonstration, and you’ll see how it works—and that it does work.
