Troubleshoot Outlook performance issues – Exchange/Office 365

It is not the first, and it will not be the last client that ask me what to do to fix Outlook performance issues.

Dennis from blogoffice365.com has written an article that mirrors what I usually recommend to my customers.

Here it is Dennis fantastic post. To see the original post click here.

When users migrated to Office 365 complain about performance, it’s because they are using many shared mailboxes and calendars mostly or have a significant personal mailbox (5GB+). However, with some simple tricks, you can increase performance quite a bit for them.

Tips to increase Outlook performance

1. First of all, you can disable Hardware Graphics Acceleration in Outlook because most graphics cards cannot correctly handle this setting. Especially switching between calendars and mailboxes can increase performance by disabling this setting. These can be done in Outlook 2013/2016 by going to file, options and select the advanced tab.
2. If users are using many shared mailboxes or public folders, it is highly recommended to de-check the download shared folders option in Outlook. By default, Outlook wants to cache every folder of every (shared) mailbox to your local OST file. You can disable this setting in your account settings.
3. Outlook 2013/2016 wants to cache 12 months of emails if you use it in caching mode. Recommended is changing this to let’s say 3 months for a “normal” size mailbox.
4. I have seen companies using antivirus solutions scanning every file opened by a user. However, when opening Outlook, the OST file is being scanned as well causing very long startup times for Outlook.
5. If you have Enterprise licenses for Office 365 and you use the Online Archive/In-Place-Archive functionality when users have large mailboxes. Online Archives will not cache emails to the local OST file so your Outlook profile will remain small when archiving correctly. As an administrator, you can also help users by creating policies for auto-archiving if desired.
6. Outlook add-ins can significantly decrease performance, and there are some of them known for doing so like the iCloud add-in to give an example. Recommended is to disable any add-in which is not being used.
7. Limiting the number of calendars in the “My Calendars” view will improve Outlook performance as well because Outlook will scan for changes every couple of minutes. Uncheck calendars if you are not using them regularly can help keep Outlook fast(er).
8. Limit the number of emails in the root Inbox folder as this needs to be loaded directly when Outlook starts. Even creating a subfolder in the Inbox and move your emails to it will help increase performance.

Troubleshooting Outlook performance

1. With the Office 365 Client Performance Analyzer which can be downloaded here https://support.office.com/en-us/article/Office-365-Client-Performance-Analyzer-e16b0928-bd38-423b-bd4e-b8402bc106aa
   This tool can be really helpful for troubleshooting your network against Office 365. The scan can be performed on a PC with performance issues. With the above URL, you can find what settings are measured and if a value is good or not.
2. With the Microsoft Office Configuration Analyzer Tool (often referred to as OFFCAT) downloaded here https://www.microsoft.com/en-us/download/details.aspx?id=36852
   This tool will scan a user’s Outlook profile completely, and a lot of information can be retrieved afterwards when exported to a .offx file.
3. Check the connection status for Outlook. This can be 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 visible here. There is not an easy answer on what your average response time needs to be etc. but I think if you are generally under about 200-300 you should be doing ok.

Get everyone’s mailbox size with this handy Powershell cmdlet

1. Connect to Exchange Online. If you don’t know how to do this, I included this in another post which can be found here
2. Make sure you have a temp folder on your C drive and perform this cmdlet:  Get-Mailbox -ResultSize Unlimited | Get-MailboxStatistics | Select DisplayName,StorageLimitStatus,@{name=”TotalItemSize (MB)”;expression={[math]::Round(($_.TotalItemSize.ToString().Split(“(“)[1].Split(” “)[0].Replace(“,”,””)/1MB),2)}},@{name=”TotalDeletedItemSize (MB)”;expression={[math]::Round(($_.TotalDeletedItemSize.ToString().Split(“(“)[1].Split(” “)[0].Replace(“,”,””)/1MB),2)}},ItemCount,DeletedItemCount | Sort “TotalItemSize (MB)” -Descending | Export-CSV “C:\temp\AllMailboxes.csv” -NoTypeInformation
3. Now check the AllMailboxes.csv file in your temp folder. It will contain several fields, but most important the mailboxes are sorted on size now with the biggest one on top.