How is DKIM precedence determined when double signing emails?

Email marketer from EmailDrips explains that although it is possible to have multiple DKIM records it can be difficult, and generally it is better to have one DKIM record per domain. You should also be wary about exceeding DNS lookup limits.

Email marketer from Stack Overflow states that when multiple DKIM signatures are present, the receiver validates each independently. There's no inherent precedence; each valid signature contributes to the message's overall authentication.

Email marketer from Reddit shares that multiple DKIM signatures can improve your reputation as it proves more authentication.

Email marketer from MXToolbox responds that multiple DKIM signatures can provide redundancy, in case one signature fails verification, the other signature can still authenticate the message. They advise to ensure each signature is correctly configured.

Marketer from Email Geeks explains there's nothing in the DKIM specification to allow a sender to mark the order of signature evaluation. DKIM signing with the same domain as the 5322.From is a good signal. ESPs often DKIM sign using the same domain as the 5321.From; if possible, get them to white label this domain. When DKIM signing using the same domain as both From domains, additional ESP signatures have minimal influence.

Marketer from Email Geeks shares any signing domain in a signature that can serve as a meaningful signal will be used as a signal. Many filters will give more weight to more specific signals, but that weighting is dynamic rather than fixed.

Expert from Email Geeks confirms that both DKIM keys will be validated.

Expert from Spam Resource explains that each DKIM signature is independently verified. The results of these verifications are used as part of the overall authentication process. There isn't a defined precedence; rather, the presence of valid signatures adds to the message's credibility.

Expert from Word to the Wise responds that authentication is not a single process and DKIM is only a portion of it. As such multiple DKIM records would add to the layers of authentication that a message would need to pass.

Expert from Email Geeks shares that some mailbox providers care about DKIM key precedence, others don't. From experience, the order should be Network key first, then brand key.

Documentation from GitHub notes the purpose of signing with multiple DKIMs, such as when multiple mail service providers are involved. Verifiers independently evaluate each signature and the results are considered in aggregation.

Documentation from RFC Editor explains that the order in which DKIM signatures are applied to a message is not dictated by the DKIM specification. Verifiers should process signatures in the order they appear in the message's header fields.

Documentation from Authorea explains that with DKIM records there are DNS lookup limits. If you exceed these then the email can fail to deliver. Although you can have multiple DKIM records, you must still consider the lookup limits.