There are a number of ways to authenticate e-mail. The common ones are SPF (sender policy framework) and DKIM (domain keys).
For security reasons, some organizations require both of them to pass validation and not being rejected as spam or phishing attempt. For these organizations, no DKIM = e-mail invitation not reaching recipient.
The following SG support article discusses SPF, but I saw no mention of how to set up DKIM.
Do SurveyGizmo support DKIM?
(For DKIM one needs a public key, to set up the DNS txt record with the key).
Here is some more information on DKIM.
One of our Community Moderators alerted us about your post. Thank you for your question!
While we currently do not have a feature for implementing DKIM, this is something that our Development Team is working on implementing in the future (I’m not able to provide a concrete time frame at this time). Such a feature will be available to Team Edition accounts.
I hope this helps clarify!
Survey Explorer & Documentation Specialist
SurveyGizmo | http://surveygizmo.com
Please can you also notify me when DKIM is activated. Blocking through lack of DKIM access is a major concern for me in using the SG platform for my surveys.