I was trying to rotate the DKIM Key with the two different version of SmaterMail. I've been using SmarterMail for a very long long time. I used to be able to specifiy the DomainKey selector string with the format of <customer-code><three digits>._domainkey.<customer-domain>. Today, you get this random hex selector value like 8DB5A7F1B6D3E83._domainkey.<customer-domain> which you can't edit.
I would like to define the DomainKey selector name myself instead of the psedo-random hex value and would like to hear your thoughts.
The other thing you should be aware with DKIM Public Keys, from a management perspective, it is recommended that you rotate the private key from time to time, however, you want to preserve the old public key such that older eMails can be checked against older DKIM Public Keys for validation.