Why Apple Mail so----w slo--w???

Just wondering if any of the members know why my Apple Mail is so slow? I have done all the obvious actions such as rebuilding etc. to no avail. I can type almost a line in a new message without seeing the characters I am typing and have to wait a long time to switch between incoming mail, junk, sent etc.

Any suggestions greatly appreciated.

via ehMac.ca http://ift.tt/2zyRH54