cached mode for outlook 2013

Hi Experts,

We do have an Exchange 2010 SP3 organization where most of users use outlook 2010 on cached mode. There are also some clients using outlook 2013.

Now, we are in the process of introducing new outlook clients [profile and new version of 2013] and I would like to know what are the pros and cons of implementing a new GPO to setup cached mode for new and existing Outlook profiles (outlook 2013) [this is for safe senders list]

According to link below, we should add a couple of keys to complete the GPO

Add registry subkey for safe senders list for Outlook 2010 & 2013


Any advice?

Your thoughts?

Exchange environment

2 CAS&HUB VMs one for each datacenter, running Exchange 2010 SP3. OS Windows 2008 R2 latest updates.

2 MBX VMs on a DAG, one for each datacenter with same specs above
Jerry SeinfieldAsked:
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Adam FarageConnect With a Mentor Enterprise ArchCommented:
The safe sender and block sender listings for Exchange users are synced to the server and stored on the local mailbox, so I am unaware of anything that could change with that. I also do not think you can say "if your cached use the safe senders list" but I could be wrong.

As for the GPO, the ADMX template is the only supported way.

Hopes this help ;)
Stelian StanNetwork AdministratorCommented:
You can also have a look on this link to setup Cash Mode.

By having Outlook in Cash Mode it will improve your Exchange performance. More information on the link provided above.
Jerry SeinfieldAuthor Commented:
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Adam FarageConnect With a Mentor Enterprise ArchCommented:
... its Cached mode ... not Cash mode and the user did not request on how to set it up. He wants to know the benefits.

Here are a few benefits of cached mode...

- If your Exchange server goes down for whatever reason, the user will have there last synced emails within a file called an OST. That OST file will allow them to gain access to there current mail (cannot send / receive without the exchange server online) and also queue mail to be picked up by the Mailbox role (mail submission service) whenever the Exchange server comes back online.

- Online mode consumes a lot more bandwidth along with CAS / Mailbox resources. You might be asking why, and that is because a consistent connection between the CAS/Mailbox and client must be opened while Outlook is opened while within Online mode. If you are within Cached mode, what happens is the Mailbox role (mail submission service) triggers a MAPI flag when something is changed, and then a new connection is spawned. You will not only save your Exchange server resources, but also your network resources. A win win right there.

The only downfall of Cached exchange mode would be that someone can walk away with an OST file and purchase a program to turn that OST file into a PST file. The likelihood of this is rare, but can occur. Just be aware that is the only downside I can possibly think of.

As for your registry commands above, that is for the junk email filter settings. For the Outlook junk filter to work the Exchange / Outlook encryption needs to be turned on (Within Account Settings > Change Settings (Current Exchange Email) > More Settings.. > under the Security tab there is a checkbox that says "Encrypt data between Microsoft Exchange and Outlook". This must be checked). This is probably a bug and something I have ran into recently with a client and MSFT has confirmed. Keep this in mind also, so if you turned off CAS Client encryption (on by default in Exchange 2010 SP3), and you want to use the Junk email filter settings on your Outlook client you better turn that back on.

As for setting up forced cached mode, you would use the Office Configuration Tool. You can read more about that here:

There is no "Registry" key to setup, at least none that I know of. If you can find one, I would love to know it.. seriously! :D

Hope this helps out, and remember.... its cached exchange mode, not cash mode...
Jerry SeinfieldAuthor Commented:
Thanks for the explanation

Can you please provide your thoughts in terms of applying a GPO to setup cached mode for the new and existing outlook 2013 profiles?

What will happen with the new and old profiles once the GPO has been deployed?

Any major service impact? Any risk to lost some information? for example, safe senders list for each user's profile?
Adam FarageEnterprise ArchCommented:
Setting up the ADMX template is a pain, but it does the job. All it will do is say "you must be in cached mode", so any users who were not using cached mode may have a delayed startup as the OST file is created and the messages from the inbox are downloaded.

You shouldn't have an issue with the services, except a slight impact in terms of outlook changing from online to cache for a few select users. As for the safe senders list, what are you looking to do exactly? Enable it? Then you should see no influx of issue unless you explicitly block someone on accident that is an external user (you cannot block internal traffic)
Jerry SeinfieldAuthor Commented:

You mentioned that setting up the ADMX template is a pain, do you know of any other way to perform the GPO and enable cached mode for all users?

Regarding the safe sender list, we already have in place a GPO that adds a list of safe sender lists to all users in Cached mode, my concern is, if I apply a new GPO as per link above for all outlook profiles{2013&2010}, what is going to happen with the information containing on new and old profiles? what will happen with the safe sender lists added as per other GPO?
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