Outlook 365 slow or unresponsive

%3CLINGO-SUB%20id%3D%22lingo-sub-271285%22%20slang%3D%22en-US%22%3EOutlook%20365%20slow%20or%20unresponsive%3C%2FLINGO-SUB%3E%3CLINGO-BODY%20id%3D%22lingo-body-271285%22%20slang%3D%22en-US%22%3E%3CP%3EHello.%20Our%20organisation%20of%20100%2B%20users%20has%20started%20to%20find%20very%20noticeable%20slowdown%20of%20Outlook%20365.%20We%20have%20Microsoft%20365%20licenses.%20The%20problem%20occurs%20most%20often%26nbsp%3Bfor%20users%20with%20multiple%20calendars%20or%20mailboxes%20open.%20We%20have%20redundant%20Fibre400%20connections%20to%20the%20internet%20and%20have%20very%20low%20latency%20to%20CBD%20hosts%2Fpeers.%3C%2FP%3E%3CP%3E%26nbsp%3B%3C%2FP%3E%3CP%3EWe%20have%20tried%20things%20like%3A%3C%2FP%3E%3CP%3Edisable%20unused%20protocols%20(eg%20POP3)%3B%3C%2FP%3E%3CP%3Eturn%20off%20offline%20caching%20of%20shared%20mailboxes%3B%20and%26nbsp%3B%3C%2FP%3E%3CP%3Easking%20users%20to%20minimise%20the%20number%20of%20calendars%20%2F%20mailboxes%20visible%20at%20any%20one%20time.%3C%2FP%3E%3CP%3E%26nbsp%3B%3C%2FP%3E%3CP%3EHowever%20we%20still%20have%20performance%20issues%20and%20it%20seems%20to%20be%20getting%20worse%20not%20better.%3C%2FP%3E%3CP%3E%26nbsp%3B%3C%2FP%3E%3CP%3EDoes%20anyone%20have%20a%20similar%20experience%20or%20sugggestions%20to%20improve%20this%3F%3C%2FP%3E%3CP%3E%26nbsp%3B%3C%2FP%3E%3CP%3EThanks%20in%20advance%2C%3C%2FP%3E%3CP%3ETim%3C%2FP%3E%3CP%3E%26nbsp%3B%3C%2FP%3E%3C%2FLINGO-BODY%3E%3CLINGO-LABS%20id%3D%22lingo-labs-271285%22%20slang%3D%22en-US%22%3E%3CLINGO-LABEL%3EOffice%20365%3C%2FLINGO-LABEL%3E%3C%2FLINGO-LABS%3E%3CLINGO-SUB%20id%3D%22lingo-sub-271619%22%20slang%3D%22en-US%22%3ERe%3A%20Outlook%20365%20slow%20or%20unresponsive%3C%2FLINGO-SUB%3E%3CLINGO-BODY%20id%3D%22lingo-body-271619%22%20slang%3D%22en-US%22%3E%3CP%3EDefine%20%22visible%22%3F%20If%20they%20are%20added%20to%20the%20same%20Outlook%20profile%2C%20they%20are%20still%20being%20synced%20in%20the%20background%20regardless%20of%20whether%20you%20have%20the%20checkbox%20ticked.%20If%20it's%20a%20Calendar%20you%20rarely%20access%2C%20it's%20best%20to%20delete%20it%20from%20Outlook%2C%20and%20only%20open%20it%20the%20next%20time%20you%20need%20it%2C%20and%20the%20same%20goes%20for%20Shared%20mailboxes.%20Switching%20off%20cached%20mode%20can%20help%20with%20the%20OST%20file%20growth%2C%20but%20it's%20most%20effective%20if%20you%20combine%20it%20with%20creating%20a%20new%20profile%2C%20otherwise%20space%20is%20not%20immediately%20cleaned%20(compacting%20the%20OST%20might%20help).%20But%20in%20general%2C%20disabling%20cached%20mode%20might%20lead%20to%20noticeable%20slowness%2C%20especially%20when%20trying%20to%20work%20with%20large%20mailboxes%20(large%20in%20size%20or%20in%20number%20of%20folders).%3C%2FP%3E%0A%3CP%3E%26nbsp%3B%3C%2FP%3E%0A%3CP%3EI%20would%20recommend%20keeping%20the%20main%20Outlook%20profile%20as%20clean%20from%20shared%20mailboxes%2Fcalendars%20as%20possible.%20You%20can%20create%20a%20second%20profile%20and%20switch%20to%20it%20when%20needed%2C%20or%20you%20can%20just%20use%20OWA%20to%20access%20any%20shared%20mailbox%2Fcalendar%20that%20you%20do%20not%20need%20day-to-day%20access%20to.%20Reducing%20the%20size%20of%20shared%20mailboxes%20as%20well%20as%20the%20number%20of%20folders%20in%20them%20should%20also%20help%2C%20but%20even%20with%20small%20sizes%20it%20can%20add%20up%20when%20you%20have%20multiple%20added%20to%20the%20same%20profile.%3C%2FP%3E%3C%2FLINGO-BODY%3E
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Visitor

Hello. Our organisation of 100+ users has started to find very noticeable slowdown of Outlook 365. We have Microsoft 365 licenses. The problem occurs most often for users with multiple calendars or mailboxes open. We have redundant Fibre400 connections to the internet and have very low latency to CBD hosts/peers.

 

We have tried things like:

disable unused protocols (eg POP3);

turn off offline caching of shared mailboxes; and 

asking users to minimise the number of calendars / mailboxes visible at any one time.

 

However we still have performance issues and it seems to be getting worse not better.

 

Does anyone have a similar experience or sugggestions to improve this?

 

Thanks in advance,

Tim

 

1 Reply
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Define "visible"? If they are added to the same Outlook profile, they are still being synced in the background regardless of whether you have the checkbox ticked. If it's a Calendar you rarely access, it's best to delete it from Outlook, and only open it the next time you need it, and the same goes for Shared mailboxes. Switching off cached mode can help with the OST file growth, but it's most effective if you combine it with creating a new profile, otherwise space is not immediately cleaned (compacting the OST might help). But in general, disabling cached mode might lead to noticeable slowness, especially when trying to work with large mailboxes (large in size or in number of folders).

 

I would recommend keeping the main Outlook profile as clean from shared mailboxes/calendars as possible. You can create a second profile and switch to it when needed, or you can just use OWA to access any shared mailbox/calendar that you do not need day-to-day access to. Reducing the size of shared mailboxes as well as the number of folders in them should also help, but even with small sizes it can add up when you have multiple added to the same profile.