Are you well? " I'm sorry that I didn't write a email to you yesterday because I was ill, but it looks like you will not be worried about me, but you may be busy with your work.
Are you OK? I am sorry I did not write my email to you yesterday because I was sick, but it seems that you are not as concerned about me. However, you may be busy with your work.
How are you?? I'm sorry I didn't write an e-mail to you yesterday, because I was sick, but it looks like you won't be worried about me But you may be busy with your work