You can use DKIM wizards to generate your DKIM public and private key pair. There are a lot of DKIM wizards, however, Port 25 is a good option.
Follow these steps to generate DKIM keys using Port 25’s site:
- Use Port 25 to enter the From Domain that you are authenticating.
- Enter the selector name. Choose a selector name that describes the type of email you are sending, such as marketing or newsletter. You should also standardize your selector names for ease of tracking.
- Choose 1024 bits or 2048 bits for your desired key size. Due to DKIM specification, make sure your key is at least 1024 bits.
- Select Create Keys.
Here is a link to the Port 25 tool mentioned in this article: Port 25