I'm looking to use EWS to subscribe to a very large number of Project mailboxes within our Exchange 2010 R2 Environment. So far I have successfully written a C# console application which subscribes to multiple mailboxes and collects the required emails from the required mailboxes.
To do this, I create one Exchange Service, using a service account which has permissions in exchange to administer the mailboxes, I haven't used impersonation at all for this. From there I then add multiple streaming subscriptions to a streaming subscription connection and set it off. On notification, it checks the ID of the subscription matches the subscription that fired the notification and it sets to work on collecting the emails. That works fine for a small number of mailboxes (203 to be precise), my concern is when scaling this up dramatically.
My question really is whether this is the best way of achieving this. The subscriptions count will potentially grow 1000+ mailboxes per month with figures quoted at 10000 – 30000 subscriptions at any one time. When this is scaled up to these huge numbers, I want to know that it will work and what limitations there might be. I wonder if anyone has any experience doing this and can offer me any advice to avoid me going too far down a potential dead end.
I know that E2013 offers grouping of subscriptions which may be more specific to my needs, but my organisation won't be migrating to E2013, instead looking to E2016 online in 2-3 years time.
Many Thanks
