DKIM stands for DomainKeys Identified Mail and is a method for associating a domain name to an email message (Wikipedia)
If you don’t have a verified domain and you have enabled the DKIM checkbox on the settings page you get a big red box an white input field.
It shows the encryption type (k=rsa) and the public key (p=MIIBIjANBgkqhki…xzoKBxqkQIDAQAB)
To know how DKIM works a short story:
The email program (Mailster) signs each outgoing mail with a signature based on the private key. The receiver (like gmail, hotmail or Apple mail) reads this signature and “ask” the domain for the public key. Since the public key is generated with the private key the receiver can now verify (with the public key from the domain and the signature from the private key) the mail.
If you webpage is for instance http://www.example.com so your domain is “example.com”
Now you have to add an entry as new TXT records with the value “mailster._domainkey.example.com” and the value “k=rsa;p=MIIBIjANBgkqhki…xzoKBxqkQIDAQAB”
How to add TXT records at your domain is up to your domain host. Please ask your provider for help. Some hosts don’t allow to add name records at all.
Here’s a list of popular providers and how to get to their DNS settings:
- 1&1: Add or Remove TXT Records
- Bluehost: Modify a DNS record
- Cloudflare: SPF, DKIM
- Dreamhost: SPF, DKIM
- Hostgator: Manage DNS records
- HostMonster: Modify your DNS records
- Hover: Edit DNS Record
- Namecheap: SPF & DKIM
- Network Solutions: Edit DNS Record
If you have setup your TXT records correctly you will see a green box on the settings page.
Please keep in mind that updates often takes up to 48 hours but usually are available within 30 minutes