Table of Contents

Best Practices and Recommendations


The following are some best practices or recommendations we strongly recommend you to follow before you start any Office 365 Exchange Online backup and restore.


Temporary Directory Folder Location


Temporary directory folder is used by CloudBacko Pro for storing backup set index files and any incremental or differential backup files generated during a backup job. To ensure optimal backup/restoration performance, it is recommended that the temporary directory folder is set to a local drive with sufficient free disk space.

Performance Recommendations


Consider the following best practices for optimized performance of the backup operations:

Individual Mail Object Size


Office 365 Exchange Online service has set a size limit for individual mail object to be uploaded. Considering the size of the mail object may become larger as a result of the transcoding process when it is being sent out, we strongly recommend you to keep individual mail object no larger than 80MB if you definitely want it to be backed up.

Backup Destination


To provide maximum data protection and flexible restore options, it is recommended to configure:

Large amount of Mailboxes to Backup


It is recommended to divide the mailboxes into multiple backup sets. By default, the Office 365 Exchange online backup module can back up a maximum of 4 mailboxes concurrently (4 concurrent backup threads), while backing up a maximum of 4 mail items concurrently per mailbox (4 concurrent backup threads). Therefore, each backup set supports a maximum of 4×4=16 backup threads at a time. By splitting up all mailboxes into separate backup sets, the more backup sets, the faster the backup process can achieve.

Example-1: There are 100 mailboxes needed to be backup, you can divide 20 mailboxes into one backup set.

Backup Set Name Mailbox Number
Badkup-Set-1 No.1 – 20
Badkup-Set-2 No.21 – 40
Badkup-Set-3 No.41 – 60
Badkup-Set-4 No.61 – 80
Badkup-Set-5 No.81 – 100

If there is new mailboxes added, you can create new backup set for the new mailboxes.

Example-2: There are 100 mailboxes needed to be backup, you can divide mailboxes into backup sets in alphabetic order.

Backup Set Name Mailbox Name Start with
Badkup-Set-1 A – E
Badkup-Set-2 F – J
Badkup-Set-3 K –O
Badkup-Set-4 P – T
Badkup-Set-5 U – Z

If there is new mailboxes added, you can divide the new mailboxes into the original backup sets by the corresponding alphabetic order.