If you see Outlook behaving strangely while working at home, there are a few things you might want to try. Symptoms include steadfastly refusing to connect to the server, even though everything else appears to work fine. Or connecting fine for email but hanging when you need to do something “real time” – like look up a meeting room schedule etc.
Regular ToW reader/contributor, Paul “Woody” Woodman, suggests that a series of bizarre connectivity issues are caused by some routers and having UPnP – Universal Plug and Play, a technology intended to make life easier when devices want to talk to each other through a network – enabled.
WoodysGems blog has some more details, and Phil Cross recommends the UPnP toggle as a solution to unreliable Lync and Outlook connectivity. You can always switch it back on again if the problem doesn’t go away…
The way in which Outlook connects to the Exchange Server (where your mailbox lives), is a well-known nest of vipers. 
In the Good Old Days, Outlook and Exchange maintained a direct connection with each other where everything you did on the client was fed up and down the pipe, and all the data resided on the server. Sounds great, but if anything got in the way – like a rubbish network connection, or a somewhat overloaded server – then the whole experience bogged down and got basically pretty unusable.
If you want to see how Outlook connects to the server, find the Outlook icon in your system tray, hold the CTRL key and then right-click on it. This combo displays the hitherto-hidden Connection Status… option. If you’re seeing particularly poor Outlook performance, it’s worth checking this and seeing that everything is connecting OK – try scrolling to the right and look at some of the stats to see if they look out of the ordinary…
Cached Mode salvation
In Outlook 2003, the default behaviour was changed so that Outlook operated in cached mode – in other words, everything you see in your inbox etc, has already been downloaded by Outlook, and is sitting on your PC. So you click on an attachment and it opens immediately, you sort the Inbox with 20,000 items in it, and it’s done in a jiffy.
Cached mode was a Good Thing, and it even helped isolate the user from those slow network links or servers, such that they might never notice – in fact, cached mode was the catalyst for Microsoft IT reducing the number of places where it had Exchange servers deployed internally, from nearly 100 to less than 10. If the server was further away, end users didn’t notice that the network linking Outlook and the server was slow and had a high degree of latency.
Synchronous vs Asynchronous
Synchronous means that both ends are talking to each other as part of the same, real-time conversation – like a phone call. Generally, when on the phone, you’re either listening or talking, and unless you’re one of the many clackety-clack, clickety-click typists and mouseists who inhabit Lync conference calls, you pretty much don’t do anything else whilst you’re deeply engaged. The old way of Outlook <-> Exchange comms was entirely synchronous. Asynchronous, on the other hand, is more like a text message – you fire it off, and assume that at some stage (whilst you get on with other stuff in the meantime), you’ll get a response.
Well, the Outlook cached mode is an odd mix of both of these – the majority is async, as Outlook is talking to the Exchange Server in the background, bringing down new emails and attachments and the like, but you don’t necessarily know – since most of your interaction is with a local copy of the data, the email won’t plop into your inbox until it’s been downloaded already, meaning it could’ve taken 5 minutes to download and you wouldn’t have noticed.
Where things get interesting is when Outlook has to do synchronous things – such as displaying parts of the address book. If you open the GAL and look at a person’s details, most of the content is coming from a cached copy of the common attributes, however there are a few that are not cached and will only be shown when Outlook has had a chance to have a good ol’ fashioned synchronous chat with the server. Such activities could be looking up someone’s org structure, or what DLs they’re a member of – things you don’t really think twice about when on a fast network but if you’re at home, might be a lot more noticeable.
When you embark on certain synchronous operations in Outlook, the whole application is wont to freeze (with dire Not Responding warnings in the window title) should the network start to go south, or just if the person in question is on the other side of the world and you might be communicating 
with a very remote server. If you get this far (Not Responding, all Outlook windows go a milky white colour, your cursor changes to the Circle of Hope etc) and start to panic as you haven’t saved that email you’ve been writing for the last half hour, then help may be at hand. A cure can be to right-click on the Outlook icon in the task bar, and choose Cancel Server Request from the pop up menu. You may need to do several of these in order to truly make Outlook back down, but it often resumes ordinary connectivity to the application, even if the task you asked it to do (which caused the flat spin/heading out to sea moment) didn’t complete.
