I have several forms on my site that use routing between a small number of addresses (2-3) that work flawlessly. These forms were created on an older version of Gravity Forms, if it matters. A new form created on the latest version of Gravity Forms has routing between 10 addresses, and no routed notifications are sent. When using non-routed notifications, everything behaves as expected.
More information:
- sendmail configuration is not the problem as routing works with all other forms
- it has been tested with @gmail.com, @hotmail.com, and @<mydomain>.com addresses. All destination addresses experience the same issue.