DKIM adds a cryptographic signature to outgoing email, proving the message wasn't altered in transit and really came from the claimed domain's mail server.
Gmail, Outlook, and Yahoo all weight DKIM heavily in spam filtering decisions (especially after Google/Yahoo's 2024 sender requirements). No DKIM means material deliverability risk at scale.
DKIM key not rotated after an ESP migration, selector record pointing to the wrong CNAME, signing with an expired key.
Run a free, instant audit of DKIM and every other authentication record on any domain.
Run a Free DKIM CheckDKIM selector names are often ESP-specific fingerprints — this is part of how CompetitorInbox's ESP detection works without ever seeing the competitor's actual account.