Incoming e-mails do not always appear in the inbox when they arrive.

Incoming e-mails do not always appear in the inbox when they arrive. They always do appear but there are often delays, sometimes of a few minutes, sometimes of several hours, and sometimes of many hours. At the end of the delay they always do appear, with the time at which they were sent indicated, even though that time is earlier than the time at which they appear in my inbox. I have sometimes sent e-mails to myself, as tests -- and these are also often delayed for five or ten minutes. I am not aware of any actions that I take that precipitates either the start or the end of the delay.