Domain Keys Identified Mail (DKIM) is an email authentication method by which you can improve email deliverability. With this feature implemented, users can now authorize Zoho Survey to send emails on their behalf. This increases the chances of them being delivered without landing in spam folders when the custom sender address is used in the 'From' field, as in trigger emails. However, please note that this configuration doesn't guarantee 100% delivery of the emails, as it's ultimately the receiver's discretion whether to mark the email as spam or not.