receive mail internal too slow from Exchange 2013
We have noticed that when we send an internal email to a group, it takes time to receive an email. Example if I use my email to send to Everyone (500 emails) with no attachment about 50KB it takes 20 minutes for everyone to receive. However, If I send it at the same time to my Hotmail account, it only takes less than 30 seconds to receive.
Is it perhaps RPC over HTTPs (aka Outlook Anywhere) that is the cause? When people are in their office (ie logged in to the domain), they don't need RPC over HTTPs and I have a vague memory that this feels like you got a delay.
You will see this in the settings for how Outlook communicates with Exchange (look in Account Settings).
I'm not a techical expert myself, but I know that you can control these settings for everyone in your office through a Group Policy (GPO).