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Posts Tagged ‘dkim’

High Volume Bulk Email: Key Ingredients for Good Deliverability

Monday, January 15th, 2018

How do you ensure your messages make it into your recipients’ INBOXes?

Deliverability is key to anyone sending newsletters, announcements, notifications, or any other type of bulk email.  As a provider of premium and bulk email services, we constantly advise customers on how they can legitimately avoid having messages marked as spam and ensure that they are not black listed. In this article, we consolidate our advice for everyone’s benefit.  This includes: ensuring you have a good mailing list, maintaining your mailing list, email message content, and reputation management techniques like SPF, DKIM, and IP anonymization.

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Save Yourself From “Yourself”: Stop Spam From Your Own Address

Friday, September 22nd, 2017

I just got junk email … from me!

It is surprisingly common for users to receive Spam email messages that appear to come from their own address (i.e. “joe@domain.com” gets a Spam email addressed so it appears to be from “joe@domain.com”).  We discussed this issue tangentially in a previous posting: Bounce Back & BackScatter Spam – “Who Stole My Email Address”?  However, many users wonder how this is even possible, while others are concerned if their Spam filters are not catching these messages.

Spam from your own email address

How can Spammers use your email address to send Spam?

The way that email works at a fundamental level, there is very little validation performed on the apparent identity of the “Sender” of an email.  Just as you could mail a letter at the post office and write any return address on it, a Spammer can compose and send an email address with any “From” email address and name.  This is in fact extremely easy to do, and Spammers use this facility with almost every message that they send.

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ARC and SMTP MTA-STS: The State of Domain-based Email Authentication – Part 3

Tuesday, September 19th, 2017

We’ll close (for now) our three part series on the state of domain-based authentication for emails by completing the story on technologies being deployed or defined to improve the security of the email ecosystem. In Part 1, we wrote about using Sender Policy Framework (SPF) and DomainKeys Identified Mail (DKIM) to authenticate the sending mail server. Part 2 described how Domain-based Message Authentication, Reporting and Conformance (DMARC) is used to provide clear guidelines for the treatment of mail that fail SPF and/or DKIM authentication.

Authenticated Received Chain

In this post, we’ll touch on two topics that are mature works in progress in the IETF, the technical standardization organization that has brought us so much of the protocols that govern the internet. The first technology is Authenticated Received Chain (ARC), defined to handle the shortcomings of SPF and DKIM when used with mail forwarders or mailing lists. The second technology is about correcting the lack of security between Message Transfer Agents (MTA), and a solution to enforce strict transport layer security for SMTP message transfer between MTAs.

It’s worth reiterating again that all these technologies are building blocks, and only when used and deployed collectively by the entire ecosystem can we hope to create the barriers needed to thwart fake emails and mail surveillance by malicious actors.

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DMARC: The State of Domain-based Email Authentication – Part 2

Monday, September 11th, 2017

Building a safer email ecosystem with DMARC

In our previous post, we described two techniques for authenticating an email sender:

  • Sender Policy Framework (SPF), IETF RFC 7208, which verifies if the sending MTA is indeed authorized to send mail on behalf of a domain; and
  • DomainKeys Identified Mail (DKIM), IETF RFC 6376, where a domain shows “ownership” of a mail it sends by signing portions of it so that critical aspects cannot be forged by intermediaries.

Like most technologies, these are just individual weapons in the arsenal for fighting phishing and spam. Weapons, like all tools, need to be properly used if they are to be effective. Unfortunately, as we described in the earlier post, both SPF and DKIM are deployed in a manner that reduces their usefulness. With SPF, the validation policy set by the sender is often chosen in a manner that leaves handling authentication failures at the discretion of the recipient. DKIM, on the other hand, does not even have an explicit policy directive set by the sender. Moreover, in a heterogeneous mail environment, some perfectly legitimate MTAs might not be capable of signing messages.

Building a safer email system with DMARC

Thus, receivers in actual deployments tend to “soft fail” any SPF and/or DKIM validation failures as there are reasonable situations when legitimate mail can fail such checks. A common example is forwarded mail (which fails SPF), or mail sent via a mailing list (which fails DKIM). Mail providers consider it better to deliver most mail (even if some are fake or spammy) rather than risk dropping legitimate mail. Thus, neither of these techniques individually or combined provide clear guidance to receivers, and the resulting actions can be inconsistent.

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Self-Addressed Spoofed Email: How to Shut Down Spam

Thursday, May 11th, 2017

Spam messages coming from… your own email? This may sound like a cheesy movie plot, but this form of spam, known as “spoofing,” can have horrifying consequences if they result in compromised security, stolen data, or malware on your company’s machines. Read on to find out how to snuff out spoofing and help everyone avoid these attacks in the future.

Forged Email

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