Showing posts from September, 2016

Is the internet ready for DMARC with p=reject?


DMARC is an email policy that builds on DKIM and SPF to provide a way for email senders to declare: "All email from this domain comes from this set of servers (SPF), and is signed using these public keys (DKIM)."

It's nice and well that we are finally able to do that, but DMARC comes with 3 modes of operation: p=reject, p=quarantine, and p=none. These modes suggest what a recipient should do if an incoming email doesn't match the sender domain's DMARC criteria, either due to signature failure (DKIM) or incorrect sending server (SPF). The default mode, p=none, boils down to "do whatever, maybe this helps you guess if the email is spam". The mode p=quarantine treats the email as spam, and p=reject is supposed to cause the message to be rejected at the point of ESMTP delivery.

Well, I tried p=reject, and it kinda works. Mostly. Except in the following situations:
If you send to any mailing lists from your domain. Your messages may be DKIM signed, but wh…

Lock-step refactoring

This may seem obvious, but I am biased to avoid saying things that are obvious to me, and then things don't get said that are worth saying.

A nice thing about statically typed languages, like C++, is how you can use the compiler to help refactor.

Code often needs to be refactored. If it is not, it gets harder to fix issues and implement new features. When this happens, the temptation arises to throw the code away and write new code, but this is almost always a mistake. The correct process is to refactor code that works, to disentangle anything that needs disentangling, so that improvement becomes easier.

When there is existing code you can use, you should only ever write new code if you're willing to go through the entire years-long process of how it needs to work, and why it needs to work that way. Otherwise, use existing code, and keep improving it.

Refactoring is scary. It is scary because you have this hairy code, and you're concerned that any change you make to it wil…