I have a customer who has certain users who complain about dead air when accessing their Unity mailbox through the phone. They are on Unified Messaging. Unity 5 with Exchange 2K7. They can call in, get dead air, call back in and they get right int.
This customer has huge mailboxes. 5-10 Gigs is very common and it seems like the people that have issues have upwards of 50,000 messages.
Now I know the official documented limit is 100MB in the Inbox. And my suspicion is that they dead air is Unity indexing the box. Then is gets cached for a certain amount of time and when the person calls back in that is why it gets in.
So this is all my theoretical assumptions. So has anyone else ever run across this and gotten and official technical explanation that I can provide the customer. I have applied all the ES's that would speed up the process and tweaked Exchange and Unity both to their limit. So I think I have done all I can do outside of having users delete messages.