Why is Outlook Running So Slowly on Our RDS Farm?
Asked by
TechieTommy12
Hi everyone! I'm reaching out for some assistance regarding a performance issue we're facing with Outlook on our RDS Farm running Windows Server 2019. We have about 250 Windows users connecting from their Windows 11 notebooks, and unfortunately, since the 2019 version doesn't support the new Outlook, we're stuck with Outlook Classic.
Previously, opening an email took about 3 seconds, but just last week, that time ballooned to 4-6 seconds when in online mode. This issue is quite specific since online mode is the only one affected, and it's causing a real headache for our entire company. To give you a clearer picture, here's how performance looks:
- Local devices: All versions of Outlook (Classic, New, OWA) are speedy in both cached and online modes.
- RDS OWA is fast.
- RDS Outlook Classic is quick in cached mode but slow in online mode.
We've ensured that all Office Apps are getting the monthly updates, and all our RDS servers are fully updated as well. Our mail signature solution embeds pictures directly in the HTML code. Given that local Outlook and OWA are performing well, I highly doubt the signature is the issue. This slowdown started about 2 weeks ago, and the only thing that changed was some Windows updates. Does anyone have any clues on what could be causing this slowdown with Outlook on our RDS farm?
Answers
Is there a chance that your WAN connection has per-user rate limits causing the slowdown? Just throwing that out there, but a 4-6 second load time isn't ideal but not terrible overall. It could be manageable with some tweaks.
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Outlook Classic can really struggle in non-cached mode, especially on an RDS setup. If it's a requirement to use Classic, definitely consider switching to cached mode if possible. It makes a huge difference in performance. In an ideal setup, you really shouldn't be using Classic without it!
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Yeah, online mode with Outlook Classic can be pretty slow. If you can switch to cached mode, that would drastically improve things. Another thing to consider is checking the size of your mailboxes; keeping them small helps too!
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Just a heads-up, if you're using RDS, placing OST files on a network share is supported. You could try enabling cached mode for primary mailboxes while keeping it off for shared ones. Also, for most users, a 6-month cache duration usually works well.
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Have you checked if you have enough storage to enable cached mode? It sounds like you might be dealing with either slow internet speeds or issues from the Microsoft servers. Try looking at the connection status by Ctrl-right-clicking the Outlook icon; that could give you some clue about any failures or high response times.
GadgetGuru23: Good point! Keeping an eye on connection status can reveal a lot about what's going wrong.
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Answers are reviewed before publication.
DailyFixJoe45: Totally agree! Online mode just isn't built for efficient use; cached mode is necessary unless your mailbox is really small.