I have access to a spare virtual machine and am looking to create a secondary / cache version of our exchange server which users can access their mail through, I'm hoping to free up so bandwidth on our main internet line out of the office since our primary mail is located offsite and hopefully shorten load times for mail box's when they get re-synced, Or is the only similar thing like this is when using cache mode in outlook ?

Our primary server is windows 2008 and exchange 2010, the secondary server is 2012 and has no version of exchange installed yet as I cannot find much on this topic online.

We only have one office site, but our mail server is currently being hosted remotely, which is why I was looking into having a locally hosted email server to lessen the load on the internet, while keeping the remote email server.

As mentioned in the comments, on of the reason I'm trying to avoid cache in exchange, is with some of our group mail accounts we had some issues with mail not being processed in real time, and causing other users to not see sent items / tagged mail


Not possible. No such feature exists, which is why you cannot find anything.

You could use a DAG. However for a DAG to work both sides need to be the same version of Windows. On Windows 2008 that means Enterprise edition of Windows Server (changing the version with Exchange installed is not supported). If you migrate to Windows 2012 then you can use standard edition on both sides.

However even if you setup a DAG, users will still connect to your main site to pick up email, so there will be no bandwidth saving. You could put all of your email in the other location, but then office based people would be limited by the bandwidth available to you to the remote server. Active/Active isn't going to work very well (where you have some mailboxes in the office and others in remote site in the same DAG).

Are you not using Outlook cached mode at the moment? Outlook is designed to use that function, unless of course you are using RDP.

  • Some of our users are using cache mode at the moment, however we got a mixture of thin clients and desktops and been having some issues with the cache mode updating the email server in real time, We have had some issues where in group mail accounts people have modified emails / moved, which resulted in having only updated on the client and not the server. this did not change for other users using the same group mail account. hence the reason I'm looking into this at the moment. – user2999118 Mar 24 '17 at 12:44

At first: there is no "Read Only" Exchange server as outlined in your question. So this wouldn´t work

However you can use the additional server as an additional exchange server in your DAG. Check the MS Documents for site resilience and high availability (e.g here or here).

Keep noted that both exchange server need to replicate the content. So not sure if that is a big improvement to you when both server (the new and old one) use your small internet line to sync with each other.

The best way to improve you situation would be to use the Exchange Cache Mode. Then the stuff is mostly keep on the users PCs and only new elements are synced. This should improve your situation and might lower the traffic.

You might also wish to check the Exchange Client Throttling Policies. If you have some users who "overbooked" the environment you might wish to come up with a fine tuned policy for them to avoid they use more resourced as others.


You said you have issues with the Exchange cache mode. I would prefer when you start troubleshooting that. Maybe the users might understand that emails aren´t chat and that there will be always a delay. I know it would be hard here in the modern world.

  • I have added a bit more details to my question, however in this case where we have 90 % of our mail being accessed on site A, but have our mail at site B, would creating a Dag server on site A be beneficial to lessen the throughput on the internet link ? Or would all clients still need to be synced from the primary / originally mail server on site B, even if its just reading the mail without making changes or sending mail ? – user2999118 Mar 24 '17 at 12:52
  • An Exchange DAG is more Active/Passive. It didn´t help you with saving "traffic". The users will still pick up emails in the main office as outlined in the linked documents above. – BastianW Mar 24 '17 at 13:08
  • Thanks for the feedback, ill be looking into Exchange Client Throttling Policies afterwards and and try to fix the cache mode issue when i get in to the office, however one last thing, if I do create a DAG server can they be swapped to a Main mail server ? if so could I do what I said before but in reverse ? so Mail at A , DAG at remote and would it be possible to set up automatically fail over for if A fails ? or do you believe the there would be no benefits in regards to performance and responsiveness doing this ? – user2999118 Mar 24 '17 at 13:29
  • There is no DAG server ist a kind of cluster/Group. DAG = (Database Available Group). So one DAG can contain two Exchange Mailbox Server. then you can choose if the Exchange server 1 or 2 inside the DAG has the mailbox mounted. – BastianW Mar 24 '17 at 13:35

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