What DMARC Protects You From, and What It Does Not

What DMARC Protects You From, and What It Does Not(senderledger.com)

38 points by adulion 3 hours ago | 11 comments

sam_lowry_ 2 hours ago |

> Every email carries two "from" addresses

I made a presentation about exactly the same subject many years ago, but I was not shy of separating the SMTP protocol (RFC 821 and the following ) and the email message (RFC 822 and the following).

It makes the link between SPF, DKIM and DMARC much clearer.

Anyway. The article covers just the bare minimum, and in the most obscure way.

For those interested in the inner workings of contemporary email delivery... I recommend the posts by Alex Shakhov on LinkedIn https://www.linkedin.com/in/alexshakhov/ (Yes, there is still meaningful content on LinkedIn, it's just vanishingly rare)

philosopherNoob 19 minutes ago | |

Are those posts available without logging in? This sounds like good stuff but I can’t access it.

sam_lowry_ 10 minutes ago | | |

I think he reposts them on his consulting page https://www.sh.consulting/blog and no, I am not affiliated. Just keeping an eye on the email deliverability topic as a hoppy.

avian 1 hour ago |

Vaguely related question: what is the go-to open DMARC check implementation these days? I mean the part that checks _received_ mail against DMARC rules. It used to be opendmarc, but it seems people have been dropping it for a while because of history of breaking changes and general lack of good stewardship [1]. Anyone using pydmarc [2]?

It's hard to find good info on this since 99% of search hits are people talking about setting up DMARC from the _sender_ side.

[1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1014058#39

[2] https://pypi.org/project/dmarc/

oogali 50 minutes ago | |

I use rspamd.

This might be a little heavy if you’re solely looking for DMARC validation, but I use the other parts of rspamd as well for inbound email.

https://rspamd.com/modules/dmarc/

For a library, I mainly write Go and I use https://github.com/emersion/go-msgauth (formerly known as go-dkim).

1over137 40 minutes ago | |

Indeed opendmarc seems practically abandonware.

rspamd is what I use.

joladev 50 minutes ago |

> Here is the part that trips people up.

It's hard to take something seriously when it's very clearly AI generated. It's just a coin toss on whether the information in the article is correct.

sylware 1 hour ago |

I think DMARC is missing email address with IPv[46] literals support. As being self-hosted, without paying the DNS mob, I am still blocked to send email to gmail.com because such email addresses do throw out of whack gogol code.

Email addresses with IPv[46] literals are intrinsincly stronger than SPF. If in the envelope or any of the 'from' headers (if my memory does not fail me, there are few more headers to scan), the IPv[46] literal does not match the actual and real IP of the SMTP server, the email is dropped, not even going into any spam folder.

Conspiracy mode: they know and are careful not to support that, in order to create a walled garden of internet messaging for them and their friends.

inigyou 55 minutes ago | |

Wasn't this removed from the email standards?