Mail search not finding messages in Inbox

Hi,

I just updated to Sierra on my MacBook Pro, and I noticed Mail is not searching properly. I know I have several emails from a particular sender in my Inbox, and when I use my own memory to recall roughly when I received the email, I can scroll down and find it. However, my memory isn't always so reliable, and I need to use the Mail search function. Even when I have the particular email open, Mail Search will not find it. I have enabled Spotlight to search everything, and Mail preferences include encrypted and Trash mail. However, this email is in fact in my Inbox. I have also restarted Mail. Any suggestions to help please?

Thanks in advance,

Rosaroo