Why the mail is crazily slow after updating the os?

Just after updating the OS with El Capitan in my Macbook Pro, I noticed that mail has lost some of the settings in terms of incoming/outgoing servers, and so that it's not receiving any new mail primarily from Hotmail. After deleting the messed up hotmail setting I added up a fresh new hotmail account to the mail, it's somewhat working now, BUT it's crazily slow. Since last 3 days still it couldn't get all the mail from my hotmail account. Please advise me how to fix it.