DKIM
A cryptographic signature attached to outbound mail.
DomainKeys Identified Mail signs each message with a private key. Mailbox providers fetch the public key from DNS and verify the signature. DKIM proves the message was not tampered with and is critical for DMARC alignment.
reading this as teams building autonomous agents
An agent stack treats email as a two-way primitive. Inbound has to arrive as structured JSON a tool call can consume, sends have to be safe to retry when a model loop repeats itself, and every action needs an audit trail. A provider without inbound parsing only solves half the problem.
Applied to dkim, that means weighing inbound parsing, idempotency keys, webhook coverage, and operating track record ahead of the rest, against inbound parsing into tool calls and model-generated sends that must not duplicate.