Students Are unable to login email from portal

i'm new in luminis and i'm facing an issue

students are not able to open email from portal but faculty and staffs are able to ,

this is the error message we are getting when student is trying to login

[2018-08-15 09:36:24,148] [ERROR] http-8080-6:/ms/Authenticate com.campuspipeline.sso.authenticator.SSOOperations.authenticateUser:220
>>> authentication failed with exception:

luminis version 4.3

please advise how to solve this issue