# Diagnose performance issues with Outlook in online mode

Office 365 may exhibit higher latency because the Exchange server is not On-Premise. You can troubleshoot latency using Outlook Connection Status, a Microsoft tool. This tool shows, among others:

- Req/Fail
- Avg Resp
- Avg Proc

For the meaning of these values, refer to Microsoft Support: [Description of the Connection Status dialog in Outlook](https://learn.microsoft.com/en-US/outlook/troubleshoot/connectivity/description-of-the-connection-status-dialog-box).

To identify possible causes on the client side, follow these troubleshooting steps in order:

1. Make sure that you meet the [prerequisites](https://docs.zivver.com/en/admin/officeplugin/troubleshooting/diagnose-performance-outlook.html#prerequisites).
2. Review the [settings in Outlook](https://docs.zivver.com/en/admin/officeplugin/troubleshooting/diagnose-performance-outlook.html#outlook-settings).
3. Examine the [actions users take in the Outlook client](https://docs.zivver.com/en/admin/officeplugin/troubleshooting/diagnose-performance-outlook.html#user-actions).
4. Review the [network components](https://docs.zivver.com/en/admin/officeplugin/troubleshooting/diagnose-performance-outlook.html#network-components).
5. Analyze network latency using the [Connection Status tool](https://learn.microsoft.com/en-US/outlook/troubleshoot/connectivity/description-of-the-connection-status-dialog-box).

## Prerequisites

- Make sure you are using a supported version of Outlook. Refer to [Microsoft Support](https://learn.microsoft.com/en-us/deployoffice/endofsupport/microsoft-365-services-connectivity).
- Make sure you are using a supported version of the Zivver Office Plugin. Refer to the [Zivver Office Plugin release notes](https://docs.zivver.com/en/user/officeplugin/references/release-notes.html).

## Outlook settings

- Ensure that Outlook 365 is running in cached mode. For more information, see Microsoft Support: [Turn on Cached Exchange Mode](https://support.microsoft.com/en-us/office/turn-on-cached-exchange-mode-7885af08-9a60-4ec3-850a-e221c1ed0c1c?ui=en-us&rs=en-us&ad=us).

- Ensure that the **Download email for the past** slider is set to a sufficiently high value. This slider determines how many days of email are cached. The fewer emails are cached, the more data must be retrieved from Online, which can increase latency.

- Update Office 365 to the latest Outlook build.

- Update the Zivver Office Plugin to the latest version.

## User actions

Review the actions that users perform in Outlook. Users may perform online actions that impact performance. Examples include:

- Comparing agendas
- Sending meeting requests
- Retrieving and sending free/busy information
- Using address books other than the local address book

## Network components

Analyze the network components that Office 365 traffic passes through. Traffic should bypass these components to reduce latency:

- Proxies
- Deep packet inspection for Office 365 endpoints
- Load balancers between Office 365 endpoints

## Latency diagnosis

Examine the [Outlook Connection Status](https://learn.microsoft.com/en-US/outlook/troubleshoot/connectivity/description-of-the-connection-status-dialog-box). To open Outlook Connection Status:

1. Press and hold the _Ctrl_ key, then select the Microsoft Outlook icon in the notification area.
2. Select **Connection Status …**

**Req/Fail**

Should be 0 (zero).

Failed requests may indicate performance issues.

**Avg Resp**

Should be 10–30 ms.

More than 100 ms can indicate noticeable performance issues.

**Avg Proc**

Should be 10–30 ms.

More than 100 ms can indicate noticeable performance issues.

Updated on 2026-06-18