You can now choose between 1024-bit and 2048-bit RSA key sizes when
creating DKIM (DomainKeys Identified Mail) keys. Before choosing a key size, research possible
limitations and security requirements, such as complying with industry-specific security
regulations like FIPS (Federal Information Processing Standards). Existing DKIM keys are set to
the 1024-bit size. You can specify the RSA key size only for new DKIM keys.
Where: This change applies to Lightning Experience, Salesforce Classic, and all versions
of the Salesforce app in all editions.
How: From Setup, enter DKIM Keys in the Quick Find box, and then
select DKIM Keys. Click Create New Key, and select
the key size.