DR and DBCR E-mail approvals not working in StarTeam-Cross Platform Client

Approver will receive an email whenever there is a new DR/DBCR is raised by requestor and approver can click on 'Approve DR/DBCR'. It will auto approve the DR/DBCR in StarTeam-Cross Platform Client. But this feature not working from a month. Approver receives the emails but auto approve feature not working when he clicks on 'Approve DR/DBCR'.

StarTeam info:

Notification Response Handler Logs showing as below,

[ERROR][connect] Error in EmailNotificationResponseReader.connect()
javax.mail.AuthenticationFailedException: AUTHENTICATE failed.
at com.sun.mail.imap.IMAPStore.protocolConnect(IMAPStore.java:732)
at javax.mail.Service.connect(Service.java:366)
at com.phh.tlm.services.starteam.EmailNotificationResponseReader.connect(EmailNotificationResponseReader.java:69)
at com.phh.tlm.services.starteam.TLMEmailNotificationResponseHandlerService.handleResponse(TLMEmailNotificationResponseHandlerService.java:399)
at com.phh.tlm.services.starteam.TLMEmailNotificationResponseHandlerService.main(TLMEmailNotificationResponseHandlerService.java:117)

Please let me know if any info required and suggest me how can I fix this issue. Thanks in advance.