# Guidelines for Exchange Online Access Nodes

Verify that the access nodes for Exchange Online meet the guidelines. Access nodes run backups and other operations.

For high availability (which is recommended for the first full backup), use 2 or more access nodes.

## With Content Indexing

If you use content indexing, use the following guidelines.

Environment | Medium | Large
--- | --- | ---
Mailboxes | 5,000 | 10,000
Messages per day | 500,000 | 1 million
Guidelines |  |
Access nodes | Normal availability: 1 High availability: 2 or more | Normal availability: 1 High availability: 2 or more
CPU or vCPU for the access nodes | 8 cores | 16 cores
RAM for the access nodes | 16 GB | 32 GB
Streams per access node | 10 | 20

## Without Content Indexing

If you do not use content indexing, use the following guidelines.

Environment | Medium | Large
--- | --- | ---
Mailboxes | 5,000 | 10,000
Messages per day | 500,000 | 1 million
Guidelines |  |
Access nodes | Normal availability: 1 High availability: 2 or more | Normal availability: 1 High availability: 2 or more
CPU or vCPU for the access nodes | 4 cores | 8 cores
RAM for the access nodes | 8 GB | 16 GB
Streams per access node | 10 | 20

## Assumptions

The guidelines are based on the following assumptions:

- The average mailbox size is 5 GB.

- The average number of messages in each mailbox is 50,000.

- The average message size is 100 KB.

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