Exchange GRT Differential backup job is not supported. Exchange GRT backup should meet following guidelines.

• GRT backup of exchange is supported only with FULL and INCREMENTAL backups
• The full and incremental backups must be targeted to the same storage type. Mixed storage is not supported.
• If the Incremental GRT backups are duplicated to tape and you want to restore from the tape backup , then it needs to duplicated back to disk again.
• Select both Full and Incremental tape based backup sets of Exchange in the duplicate backup job.