← DictionaryDKIM
also called domainkeys identified mail
A signature proving an email was authorised by the sending domain.
A signature proving the email is really from you.
What It Is
DKIM is a Technology item, filed under Email Tech. In practice it means this: a signature proving an email was authorised by the sending domain.
It is a mechanism rather than an opinion: set up properly it behaves predictably, and set up badly it fails just as predictably. That definition is deliberately narrow — the narrowness is what makes it usable.
How It's Used
You will usually meet DKIM in build decisions, tooling and the plumbing behind a working system. It rarely travels alone — expect it next to SPF, DMARC and Email Deliverability. The practical test is whether it is configured, documented and actually working.
Why It Matters
DKIM is cheap to get right early and awkward to fix late. When it is unclear, small technical debts compound into a rebuild. The businesses that treat it seriously spend less time redoing work.
It is a piece of machinery doing one job in the background. A signature proving the email is really from you.
Termshift™
How the meaning shifts depending on who is using it, and where.
In agency and in-house rooms, DKIM means exactly a signature proving an email was authorised by the sending domain.
In plain conversation it comes out as a signature proving the email is really from you.
The Bottom Line
DKIM pays off when it is specific and costs you when it is not. A signature proving the email is really from you.