Education Cloud - Trouble sending recommendations

Recommendations are not sent when both the applicant and the recommender use gmail. DKIM is Active.  The email log shows the error: 

550-5.7.26 Your email has been blocked because the sender is unauthenticated. 

550-5.7.26 Gmail requires all senders to authenticate with either SPF or DKIM. 

550-5.7.26  

550-5.7.26  Authentication results: 

550-5.7.26  DKIM = did not pass 

550-5.7.26  SPF [

] with ip: [18.135.24.81] = did not pass 

550-5.7.26