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Question

M365 Mailbox Retention

  • August 26, 2026
  • 1 reply
  • 36 views

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all,

I am configuring M365 mailbox backups.

I have created an Office 365 Plan and set “Retain deleted items for 2555 days”

I then created a Backup Plan with Primary to Disk for 365 days and synchronous AUX to Tape for 2555.

Am I correct in saying that all mailbox backups from now with be Incremental and it ignores the Backup Plan retention and keeps all mail for 2555 days on Disk & Tape !

 

Also, is there a way to run a once off Full backup ?

 

Currently on 11.36

 

Thanks

1 reply

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  • Vaulter
  • September 7, 2026

Hi ​@atitagain 

Yes you are correct Exchange mailbox retention will be controlled by “Exchange/Office 365 Plan”, 

Retain deleted items for 2555 days” setting in your Office 365 Plan controls how long deleted mailbox items are kept. This retention is enforced for deleted items only.

Storage Policy retention does not apply to this agent or any of the other Office 365 Agent

Exchange Mailbox plans determine:

https://documentation.commvault.com/2024e/software/configurations_for_exchange_mailbox_plans.html

  • How messages are archived.

  • How messages are stubbed and cleaned up.

  • How messages are deleted from the Exchange server.

  • How long messages are retained on the MediaAgent.

  • Whether messages are content indexed.

Backups for Exchange Online/Office365 apps are Forever Incremental, initial baseline will be Full.

there is no default option to run Full explicitly for this agent type

only option to enable “convert to Full” via additional settings through support or engineering team.