You take a turn, I take a turn At the SMTP level email is very much a simple line-by-line text based protocol. The client sends a command on a single line, the server responds with one or more lines (the last one marked by having a space in the fourth column), and then the client sends another command. The main exception to that is when the client sends the payload of the email. Once the server...
Captchas
Captchas – those twisty distorted words you have to decipher and type in to access a website – have been around since the 1990s. Their original purpose was to tell the difference between a human user and an automated system, by requiring the user to answer a challenge – one that was supposedly hard for computers to solve, but easy for humans. A few years later they acquired the...
SPF and TXT records and Go
A few days ago Laura noticed a bug in one of our in-house tools – it was sometimes marking an email as SPF Neutral when it should have been a valid SPF pass. I got around to debugging it today and traced it back to a bug in the Go standard library. A DNS TXT record seems pretty simple. You lookup a hostname, you get some strings back. Those strings can be used for all sorts of things, but...
Good morning DMARC
I’m thinking I may need to deploy DMARC report automation sooner rather than later.
… and so on, and on, and on for a lot further down the mailbox.
DNS Flag Day
There are quite a lot of broken DNS servers out there. I’m sure that’s no surprise to you, but some of them might be yours. And you might not notice that until your domains stop working early next year. DNS is quite an old protocol, and when it was originally specified there wasn’t really a good way to extend the protocol to add new features. That was fixed about 19 years ago...
Check your abuse addresses
Even if you have excellent policies and an effective, empowered enforcement team you can still have technical problems that can cause you to drop abuse mail, and so lose the opportunity to get a bad actor off your network before they damage your reputation further. It’s not quite as simple as “We’re seeing email in our abuse ticketing system, so everything must be fine.”...
Your idea will not work. Here is why it won’t work.
Matthew Green reminded me of an old bit of spam lore. It’s a canned response to someone’s New and Awesome and entirely unoriginal Final Ultimate Solution to the Spam Problem. It originated on the news.admin.net-abuse.email newsgroup, I think, maybe twenty years ago? While one or two details have changed it’s still applicable to most of the current generation of under-researched...
The Problem With Affiliates (2)
On Friday I mentioned spam coming from a BarkBox affiliate programme. The original email is here. It’s not terribly exciting, it’s rather typical spam of the sort sent by professional spammers. It’s validly DKIM and SPF authenticated, and DMARC-aligned. It includes invisible white-on-white padding text so that it doesn’t look like image-only spam to naive filters (using...
The Problem With Affiliates
If I see BarkBox I think Spam. That’s because, despite their marketing team effort, facebook and banner ad budget, the main place I see them advertised is via spam in my mailbox. It’s not even good spam. There’s quite a lot of it. Most of it looks much the same, other than the spammer randomizing colours. This one looks better than the black on cyan version, or any of the other...
Reading RFCs
We mention RFCs quite a lot, both explicitly (RFC 6376 is the specification for DKIM) and implicitly (the 822.From aka bounce address aka return path). And we have local copies of a bunch of them to make them easy to refer to (SMTP, MIME, Carrier Pigeons …). They use quite a lot of jargon and implicit information and metadata that’s not really explained terribly clearly anywhere...