Microsoft Office 365 Slow

Office 365 is an online (Cloud based) productivity suite that is developed by Microsoft. Office 365 contains online and offline versions of Microsoft Office, Skype for Business and Onedrive, as well as online versions of Sharepoint, Exchange and Project.

Office 365 Slow Performance
Office 365 Slow Performance

Poor Office 365 performance is all too common via the bottleneck of Internet and the Cloud. Applications that have been moved into the cloud that could be a region, continent, or an ocean away, issues such as latency and network congestion can cause poor performance for Office 365 or [any] other cloud-based applications used by home users, business’s and enterprises all around the world.

See Office 365 Outage Map

Troubleshooting: Outlook performance is slow using Office 365

When you try to use Microsoft Outlook together with Microsoft Office 365, the following issues may occur:

  • Outlook responds slowly when you try to open email messages.
  • When you send an email message, the message sits in the Outbox folder for a long time.
  • Outlook responds slowly when you try to insert an attachment. Frequently, you receive the following warning message:Outlook is retrieving information from the server

Click here to check your Microsoft 365 Service Health Status.

Cloud Adoption brings Challenges

The migration of mission-critical applications to the cloud is not a seamless transition. It does bring some problems.

Cloud Based Office
Cloud Based Office

Via the Cloud scenario, you do benefit from smoother collaboration, automatic backups, and ongoing updates and patches, however your cloud application data traffic must now compete against a broad spectrum of consumer traffic, such as e-commerce, streaming videos, and social media.

Office 365 places a somewhat heavy demand on the network resource. Office 365 requires increased bandwidth for mail synchronization with Outlook, software updates, template downloads, and data. For many organizations, this leads to a significant increase in the required internet bandwidth for Office 365. This can become a counter-productive cycle that undermines productivity.

Congestion and latency on the public Internet

Facts are, there has been an explosion of consumer and enterprise traffic over the Internet. And as a result, the pipe-line flow of the Internet has become a hotbed for congestion and packet loss, which leads to poor application (cloud) performance. And when application performance suffers, the end-user experience degrades, and the complaints are made clear enough.

Office 365 has some Microsoft specific network resource requirements needed to perform optimally. And while these specifications are clearly outlined by Microsoft, if you do not have a real view of the current status of your network, these guidelines do not amount to much you can influence.

Office 365 sluggishness is often associated with high latency between the client and the destination of the traffic. Basically any traffic that is encrypted using SSL could experience high latency. This is caused by proxy servers or intermediary devices running SSL packet inspections and decryption and re-encryption before handing the packets in a flow of traffic to their destinations.

If the traffic is routed through proxy servers, it will either go straight through and the packets are left unmodified, or it will terminate and recreate all the TCP connections that are being proxied. The latter may be one reason why your Office 365 application is slow.

Why is my network so slow?

Although you don’t have control over network performance itself, it helps to understand what’s going on behind the scenes. The Internet is enormously complex, but there are a few concepts that can help you understand the situation much better. Following the best practices in this article can help workaround performance issues and reduce frustration.

Major factors that affect network performance

Network Performance Factors
Office 365 – Network Performance Factors

Bandwidth and latency The two most important measures of network performance are bandwidth and latency:

  • Bandwidth is the rate of throughput measured in bits per second. Bigger is better. Bandwidth is like a water pipe. The larger the pipe, the more water that you can “put through” it.
  • Latency is the time it takes for content to get from a server or service to your device and is measured in milliseconds. Faster is better. Latency can be caused by a number of factors including low bandwidth, a sparse connection, or transmission time.

Common issues: Besides bandwidth and latency, other issues have an impact on network performance and are often unpredictable. Network performance can fluctuate based on the time of the day or your physical location. The network can become clogged when certain events occur that spike the use of the Internet, such as a large number of local users or a major public event. The size and complexity of the page being loaded and the number and size of files being transferred have a effect on the performance. A WiFi connection can temporarily degrade: for example, you poll a large conference meeting of thousands by requesting everyone to tweet at the same time.

Using a Satellite network? A satellite network is useful when a terrestrial network is not feasible, such as some rural areas, a cruise ship, or a remote scientific area. These networks rely on satellites positioned in a geosynchronous orbit 35,400 kilometers above the equator. However, the effective transmission actually travels about 144,800 kilometers, and so a satellite network has a slower latency (500 ms or more) than a terrestrial network (20 to 50ms). Under the best of conditions, you may not notice this latency, but for downloading large files, streaming videos, and playing games, you will. Another less common issue is “rain fade” in which heavy weather, such as during thunderstorms and blizzards, can temporarily interrupt satellite transmission.

Are you sure it’s the network?

Whenever you experience performance problems, first make sure that your device is not the root cause of the problem. There are two things you can do that might make a big improvement:

  • Make sure your device is running well and there is no malware on your computer.
  • If possible, buy more memory. Adding memory is the simplest and often most effective way to improve performance on your device. It’s especially helpful when working with large files and videos.

For more information, see Windows Performance and maintenance and Fix Windows system performance problems.

Best practices for using your browser

Your browser is your gateway to Office 365, so it can have an impact on performance, especially with the time it takes to load a page and how often you round trip to the Office 365 service.

Browsers in general

Here are some suggestions for browsers in general:

  • Disable browser add-ons that might impact performance or that you don’t really need.
  • Increase the cache size for your temporary internet files.
  • Once you have signed into your work or school account, keep the browser window open throughout the day. You can open other tabs and windows without signing in again. If you need to sign in to another account, use Private Browsing.
  • Once each page is downloaded and open, keep them open by using tabs. It’s easy to navigate between tabs and use the page later on in the day. Refresh a page only if you need the latest data on that page.
  • If a page is taking too long to open, stop the page download (press ESC) and then refresh the page (press F5).
  • When possible, reduce round trips to Office 365. For example, rather than paging through lists or libraries, use search to locate files in a large library and filtering in a list to get directly to the results you want. Or, create views that minimize page load time. For more information, see Manage large lists and libraries in Office 365.
  • If video performance is poor, you may be able to download the video and watch it on your device. A download link may be available, or you may be able to right click the video link, and select Save Target as.


Here are some suggestions for your specific browser:

Best practices for using Outlook and Outlook Web App

Reading, writing, and organizing email is a big part of everyone’s day. Both Outlook and Outlook Web App (OWA) offer offline support. Using an email app on your smart phone is another useful alternative. Use the following options that best fit your needs:

  • Upgrade to Outlook 2013 SP1 or later for substantial performance improvements over previous versions.
  • Outlook Web App lets you create offline messages, contacts, and calendar events that are uploaded when OWA is next able to connect to Office 365. For more information about setting up and using OWA in offline mode, see Using Outlook Web App offline.
  • Outlook lets you work in cached mode, in which it automatically connects whenever possible. You can have Outlook download your entire mailbox, or just a portion of it. For more information, see Turn on Cached Exchange Mode and Work offline in Outlook.
  • Outlook also offers an offline mode. To use this, you must first set up cached mode so that information from your account is copied down to your computer. In offline mode, Outlook will try to connect using the send and receive settings, or when you manually set it to work online. For more information, see Work offline to avoid data connection charges, Change send and receive settings when you work offline, and Switch from working offline to online.
  • If you have a smart phone, you can use it to triage your email and calendar over your phone carrier’s network.

Outlook Slow on Office 365? Turn on Cached Mode

If your Outlook on Office 365 seems to run slowly, turning on the Outlook Cached Mode setting may improve performance. Cached mode creates a local copy (i.e., copy on your computer) of the data stored on the Office 365 cloud. Outlook accesses this cached copy for most operations, and that speeds up response times.

If cached mode is turned off, all the data for operations is stored and retrieved from the cloud, and this potentially time-consuming process can cause sluggish performance. Another advantage of turning on cached mode is that you have access to downloaded data when you do not have a network connection. This means you can work on existing email offline until your network connection is restored.

  1. Go to Control Panel
  2. Go to Mail
  3. Select E-Mail Accounts
  4. Select the e-mail account that needs to be updated.
  5. Select Change
  6. This will open the Server Settings
  7. Under Offline Settings make sure Used Cached Exchange Mode is checked
  8. Use the slider to move how old the data that should be in the inbox.
Outlook 365 enable cached mode
Outlook 365 enable cached mode

For users with a lot of e-mail daily or large mail boxes, I suggest selecting a value of about 1-3 months based on daily needs.

Outlook users of both Office 365 and Office 2016 that have a high number of shared mailboxes and calendars or the use of large mail database (5GB or larger) will have some performance issues. The cached mode changes shown above will certainly help.

Troubleshooting Outlook performance

Microsoft have a Office 365 Support and Recovery assistant tool which can be downloaded here.

Basically, if the above Support and Recovery Assistant cannot fix a problem for you, it will some suggestions and then help you get in touch with Office 365 support.

Also, do a check on the connection status for Outlook. This is done by holding the Ctrl key and right-clicking the Outlook icon in the system tray near the clock. Select connection status. The number of outgoing connections to Office 365 will be shown. Generally, if you are average response time is under about 200-300 that is a healthy state.

Hotmail, Outlook, Office365, or Slow Response Times

f you have an account hosted by Microsoft, such as Hotmail, Outlook, Office, or, and Postbox is taking a long time to load messages (showing you a spinner), this is because Microsoft recently changed the name of their incoming server to

To fix this, update your incoming server name in account settings.


  1. Go to Preferences > Accounts
  2. Select the account that is experiencing the problem
  3. Set Incoming Server to:
  4. Close the Preferences window


  1. Go to Tools > Options > Accounts
  2. Select the account that is experiencing the problem
  3. Set Incoming Server to:
  4. Click OK

Reporting problems with Office 365

Microsoft continually improves the overall performance of Office 365 by monitoring the network, measuring bandwidth and latency, improving page load time, reducing disk I/O, redesigning pages to use Minimal Download Strategy, adding hardware to data centers and adding more data centers. For more information about checking your current status and reporting issues, see View the status of your services.

Office 2016 vs Office 365: What’s the difference?

Office 2016 vs Office 365
Office 2016 vs Office 365

If you’re looking to purchase Microsoft Office for your business, you’ve got plenty of options. But understanding difference between the options – most notably between Office 2016 and Office 365 – can be confusing.

Office 365 to Office 2016 Comparison
Office 365 to Office 2016 Comparison

The short version: Office 2016 is a version of the Office productivity suite (Word, Excel, PowerPoint, etc), typically accessed via the desktop.

Office 365 is a cloud-based subscription to a suite of programs including Office 2016. This means you have a few options for purchasing Office 2016: a stand-alone product or as part of an Office 365 subscription. For most of us, the Office 2016 is much faster, as it is NOT (heavy) cloud based consumer of network bandwidth.

What is the difference between Office 365 and Office 2019?

Microsoft Office 2019 vs Office 365
Microsoft Office 2019 vs Office 365

Office 365 is a subscription service that ensures you always have the most up-to-date modern productivity tools from Microsoft. A license for Office 365, then, is contingent on sustained payments. Halt the latter and the license is revoked. Restarting the payments restores the license. Office 365 is a cloud based service (can be slow for some networks scenarios – as discussed earlier).

Office 2019 (like Office 2016) is sold as a one-time purchase, which means you pay a single, up-front cost to get Office suite for one computer. One-time purchases are available for both PCs and Macs. One advantage is it is not heavily cloud based and is capable of better performance for those with slow internet or high latency (satellite amongst others).

Notes: Office 2019 and Office 2016 will eventually (in about October 2023) not offer any of the cloud-connected features (Microsoft-hosted Exchange, OneDrive storage and Skype for Business.) that Office 365 subscribers would see using the exact same suite.

Office 2019 standalone applications

  • Word 2019, Excel 2019, Outlook 2019, PowerPoint 2019, and Skype for Business 2019 are all available for both Windows & macOS.
  • Access 2019, Publisher 2019, Project 2019 (Standard and Professional), and Visio 2019 (Standard and Professional) are all available for Windows only.

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