Application mailbox is being migrated to Office 365 and we are trying to connect to mailbox via REST call  as the email listener is not supporting the MSGraph APIs(INC-C7351).

We have tried with REST call and it is working.

In IST environment the certificate(self signed) is shared by MSGraph team and we have used the same in the application and mailbox integration worked seamlessly.

In UAT app team has shared the certificate with MSGraph team which they have uploaded in Azure portal.

Configured the Http Proxy and Non-Proxy settings.

Facing issue while connecting to Office 365. REST connectivity test is failing with SSLHandshake exception.

Attaching the logs and the configuration settings in document.