An Exchange Information Store backup may fail periodically or continually with errors such as the following:
Checksum verification failed for [mailbox database path]. eseutil.exe returned - 1073741502 
Checksum verification timed out for [mailbox database path]. eseutil.exe returned -1 
Checksum verification for [transaction log] logs in [transaction log folder path]. Eseutil.exe returned -1032
Occasionally, these will present as warnings with later log entries indicating the checksum verification passed.
During an Exchange Information Store backup, the Backup Agent has Eseutil run a checksum of the mailbox database and transaction logs to guarantee the Exchange data is valid. It is important to note the checksum verification is performed on the shadow copy made of the Exchange data, not the live data itself. Even so, a failed checksum verification likely indicates some sort of corruption in the information store which should be addressed.
Checksums Fail When Shadow Copy Aborts
Since the checksum is run on the shadow copy, a checksum verification failure may result from the shadow copy being deleted or aborted before the checksum operation completes. This is more likely to be the case when the checksum verification times out rather than fails out.
If you see shadow copies are aborted during the backup job, try increasing the amount of shadow copy storage available.
Checksums Indicate Corrupt Data
If the checksums are failing and shadow copy issues have been ruled out, there is a good chance either the mailbox database or transaction logs are corrupt. You can try running the Eseutil checksum on the original Exchange files manually. This will give you a point of reference to establish whether the checksums fail independently or only when run by the backup software. Directions for performing the checksum can be found here.