Terms below appear throughout guides on Common Mark Certificates (CMC). Each definition is one or two sentences; follow the links in the sidebar for the full guides.
Core terms#
Common Mark Certificates (CMC)
A CMC is a lower-tier BIMI certificate introduced in 2024 for brands without a registered trademark. Eligibility requires 12 months of prior logo use or a government-issued mark. Gmail displays the logo but not the blue checkmark.
SPF
A DNS record listing servers authorized to send for a domain. Checked against the connecting IP.
DKIM
A cryptographic signature on each message, verified with a public key in DNS.
DMARC
A policy record telling receivers what to do when SPF and DKIM fail alignment, plus reporting.
Alignment
Agreement between the visible From domain and the domain that passed SPF or DKIM.
Sender reputation
A provider's running assessment of a domain or IP based on complaints, bounces, engagement, and authentication.
Inbox placement
Share of accepted mail that lands in the inbox rather than spam.
Spam trap
An address that never opted in, used to catch senders with poor list practices.
BIMI
A DNS record pointing to a brand logo displayed next to authenticated mail; requires DMARC enforcement.
Feedback loop
A provider program that reports recipient spam complaints back to the sender.
Frequently asked questions#
Which providers accept CMC?
Gmail accepts CMC as of 2024. Apple accepts VMC and CMC. Yahoo does not require a certificate.
Can I upgrade from CMC to VMC?
Yes, once the trademark registers. Reissue the certificate and update the a= tag.