Email not working.

I am having problems with email.  Have not received mails sent to me over two hours.  In addition I sent important emails out last night between 9:30-11:30 pm but this morning, when I click on these emails (either in Sent or Inbox) I get message that it is from an "unknown sender" with additional message that the email "has no content".  Very disturbing when trying to communicate with my attorney on legal matters.