You can verify your domain by adding a digital signature. This confirms that you are the owner of the domain. Additionally, with the DomainKeys Identified Mail (DKIM) process, your outgoing e-mails are signed using a private and public key. This allows the recipient's mail server to determine whether the e-mail really came from the sender address or if it has been forged.
The procedure described below requires that you already have an appropriate TXT or DKIM key, which you created using your Google account.
For adding DKIM authentication, follow the same steps above but in step 6, enter google._domainkey in the prefix text box. Then paste the TXT record value generated by your Google account into the Value text box.