Troubleshooting Connectivity Issues For Outlook For Mac
This article describes the steps for troubleshooting connectivity issues in Outlook 2016/2019/365 for Mac and New Outlook for Mac and explains why such problems may occur. For Outlook for Windows, refer to the following article Troubleshooting Connectivity Issues For Outlook For Windows
Notes:
Outlook versions of 2011 and earlier are no longer supported.
Mac OS versions older than macOS 11 (Big Sur) are no longer supported. See the full list with service status here.
Outlook for Mac is supported on the three most recent versions of macOS. When a new version of macOS is released, the Office 2019 for Mac Operating System requirements are updated such that the three most recent versions are supported: the new version of macOS and the two previous versions.
Outlook 2019/2021 supports Exchange 2013 or higher version.
New Outlook for Mac doesn't support hosted Exchange mailboxes. If you switch to the new view by accident, your Company Exchange mailbox won't show in Outlook. To bring back the Legacy view, navigate to Help > Revert to Legacy Outlook.
See the Exchange Versions And Compatible Clients article for more information and consider updating the Outlook client for Mac to the newer version.
Symptoms of connectivity issues in Outlook
When a user uses Microsoft Outlook for Mac, they might experience the following symptoms:
The Outlook status bar might be showing Connected to Microsoft Exchange or Connected, but may not sync properly.
Outlook client is Not Responding.
Outlook is slow.
Messages come with a delay in the Outlook client.
Outlook disconnects
Messages stay in the Outbox and aren't sent. However, if the user restarts Outlook, Outlook reconnects to the server, and messages are sent.
User re-creates the Outlook profile and/or reinstalls Outlook but the issue is not resolved
Here is what normal Outlook status looks like:
How to troubleshoot connectivity issues
As a first step, check if you can log in to Webmail (OWA) ( https://owa.serverdata.net ) and replicate the issue there. That will allow you to determine if your connection to the server works fine. You may get one of these error messages:
Login or password incorrect. | Verify your password is correct, ask the account administrator to reset your password if necessary or reset it via the Forgot Password option. |
Server is unavailable. | Clear browser cache, restart OWA and try again. If the server is still unavailable, run the traceroute command and provide Support with the results. |
If an issue is not replicable in OWA, then it is local to Outlook and can be caused by the following reasons:
Connection Issues
Check the Work Offline mode status
Cached Mode
Get the traceroute (tracert) details
Restart Firewall/Router
Check Configuration Settings
Corrupted entries in Keychain
Mailbox-related issues
Check the number of items per folder
Check the mailbox size
Keep the number of subfolders in Inbox and Sent Items to minimum
Software-related issues
Check for available updates
Disable add-ins in Outlook
Check the antivirus settings
To troubleshoot connectivity issues locally in Outlook, follow the steps listed below one by one and see if the problem persists after each step.
Important: Tests should be run on the affected computer while the user is experiencing connectivity issues.
Connection Issues
Working in Offline Mode
Make sure that the Work Offline mode is turned off in the affected Outlook for Mac: click on Outlook in the upper right corner if there is a checkmark next to Work Offline then you are in Offline Mode, uncheck it. Sometimes Outlook may go to Work Offline status when there are intermittent issues with the Internet connection.
Cached Mode
Unlike Outlook for Windows, Outlook for Mac always runs in Cached Mode and it is not possible to switch it to Online Mode. If the cache becomes corrupted, it will cause synchronization issues in Outlook. Users can empty this cache so Outlook can download all the items from your Exchange server again. To do it: open up Outlook > right-click the desired folder and scroll down to Properties > select Empty Cache on the General tab.
Important: This procedure deletes any information that is not synchronized with the Exchange server, including your contacts' mail certificate. Emptying the cache replaces the contents of the folder with the latest items from the Exchange server. Before emptying cache, you may want to back up your Outlook information.
In case of a large mailbox (i.e. more than 50GB, you can check your mailbox size in My Services click on Storage or admins can check it in CONTROL PANEL under Users > click on the user's Display name > Exchange > Storage Management), it is strongly recommended to archive mailbox data periodically to avoid increasing Outlook cache and its corruption. See the Mailbox-related Issues section below for more information
Run traceroute (tracert)
A traceroute is a function that traces the path from one network to another. It allows you to determine if your connection to the Exchange server is lost, and also shows where exactly that happened. Check with Support for your correct Exchange server address.
Note: Despite the fact that normal websites may be opening fine, there can be some connection lags or interruptions on a particular network segment.
Important: traceroute must be run during the time when the user is experiencing the issue from the computer that is experiencing the issue.
Go to Applications > Utilities > Terminal to run the command
If timeouts happen at the very beginning of the route, reboot your network equipment or contact ISP.
If you see asterisk signs at the end of the route contact Support. Also provided the Client Access Server (CAS) you are connecting to, browse the following link:
https://[your Exchange proxy server]/scripts/server.aspx
Note: some servers might reject ping requests so timeouts on one particular hop do not indicate an issue.
Firewall/Router
Firewall or router appliances may contribute to the latency. Try temporarily disabling the firewall and attempting to connect once again. Optionally try connecting from another network segment/location if possible and see if Outlook performance is better that way.
Check Configuration Settings
Open Outlook and go to Tools > Accounts, select the existing mailbox account, and click the Advanced button in the lower right-hand corner of the window
For more information read the article How Do I Configure Outlook 2016/2019 For Mac To Connect To Exchange Mailbox?
Remove Corrupted Entries from Keychain
If you receive an error Mail could not be received at this time, clear credential entries from Keychain:
Quit Outlook and all other Office applications.
Start Keychain Access by using one of the following methods:
Open the Finder application, click Utilities on the Go menu, and then double-click Keychain Access.
In Spotlight Search, type Keychain Access, and then double-click Keychain Access in the search results.
In the search field in Keychain Access, enter Exchange.
In the search results, select each item to view the Account that's listed at the top, and then press Delete. Repeat this step to delete all items for your Exchange account.
In the search field, enter adal.
Select all items whose type is MicrosoftOffice15_2_Data:ADAL:<GUID>, and then press Delete.
In the search field, enter office.
Select the items that are named Microsoft Office Identities Cache 2 and Microsoft Office Identities Settings 2, and then press Delete.
Quit Keychain Access.
Note: When you restart Outlook after that, you will be prompted to authenticate.
Mailbox-related Issues
Number of Items
Sometimes Mac users report that Outlook is not syncing properly (or syncing quite slowly, freezing frequently) with Exchange. The problem usually is not a connectivity issue between the mail client and the mail server, but rather a local Outlook database corruption. In many cases, Outlook does work properly with folders as large as 5,000 items and more, but decreasing the folder size can improve the performance significantly. Due to the nature of the Outlook software performance, Microsoft recommends maintaining no more than 5,000 items per folder and 500 folders total including subfolders.
Check the number of items in folders to see if they exceed the limits. To check the number of items in folders, open Outlook and select the folder. The number of items in it will be indicated in the lower-left corner of the Outlook client.
Note: the number of items cannot be checked in OWA.
Read the following Microsoft Office article for more information: Outlook is running slowly
Mailbox Size
Large mailbox size arises from the problem above – the existence of a large number of items in a folder and a huge number of folders in a mailbox. By default, the mailbox size is not limited. The size limitation is set for the whole account storage, which depends on the account plan. However, we do not recommend maintaining large mailboxes as it can lead to the constant growth of the cache data file and thus its corruption and poor Outlook performance. Mailboxes that are getting close to 50GB are considered large.
The size of the local cache file can be checked at the following location: ~/Library/Group Containers/UBF8T346G9.Office/Outlook/Outlook 15 Profiles
Note: Changing the location or using a mail identity that is located on an external hard disk or a network is not supported.
Also, the mailbox size, as well as the folder statistics, can be seen in Outlook: right-click on a mailbox > Properties > Storage.
It is important to note that Outlook is designed to be used as a mail client primarily and it is not designed to be used as a long-term archive store of a large amount of email.
Read the Knowledge Base article How To Organize A Large Mailbox for information on how to reduce the mailbox size.
Keep the Number of Subfolders in Inbox and Sent Items to Minimum
Outlook on Mac may slow down performance when there are multiple subfolders. Instead, it is preferable to create new folders on the top level. The same level as Inbox and Sent Items are for better performance.
Software-related Issues
Check for Updates
Out-of-date software is a common issue that can prevent you from sending and receiving emails. Make sure Outlook and macOS are not missing important updates.
Note: Outlook versions of 2011 and earlier are no longer supported. Mac versions older than macOS 11 (Big Sur) are no longer supported. See Exchange Versions And Compatible Clients for more information.
To update Outlook for Mac: click on Outlook on the top menu, go to Help > Check for Updates.
To update macOS: choose System Preferences from the Apple menu > Software Update > Update Now or Upgrade Now
Disable Add-ins for Outlook for Mac
Some add-ins may also load Outlook with extra work. Open the Add-ins section in Outlook and try disabling add-ins one by one to find the culprit.
To open the add-ins section in Outlook for Mac, navigate to Get Add-ins icon on the Home tab. It will redirect you to the OWA page and after logging in, the list of the add-ins will be presented there.
Antivirus
Verify if you have one and disable it to test the Outlook performance.
