[NAME, COMPANY AND ADDRESS, ex.
John Smith
XYZ Inc.
1234 First Street
Suite 567
Anycity, Anystate  85245]
 

Dear [NAME, ex. John Smith], 

I was quite upset to hear that you are feeling ill.  However, with the vigor and stamina for which you are known, I am certain you will be better in no time.  Please accept, then, my sincerest wish that you get better soon.

Sincerely,
 

[YOUR NAME, ex. Jill Jones]