Looking on the internet deeply has found these results:

This letter is to express my interest is the most popular phrase on the web.

This letter is my interest 10 results on the web	This letter is to express my interest 1541 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
It doesn't look like this phrase is very popular! The search could not find any examples on the internet.	This letter is to express my interest in the receptionist position your company has posted. Based on my superior administrative skills, I am confident that I would ... This letter is to express my interest in the position as Systems Engineer for International Widget Corporation in South America, announced in the December job ... This letter is to express my interest in the Customer Service Manager position posted on the XYZ Company web site. Your marketing department has advertised ... March 22, 2007. This letter is to express my interest in discussing a position with your firm. I believe an opportunity with your firm will provide me with priceless ...

This letter is my interest

10 results on the web

This letter is to express my interest

1541 results on the web

More popular!

It doesn't look like this phrase is very popular! The search could not find any examples on the internet.

This letter is to express my interest in the receptionist position your company has posted. Based on my superior administrative skills, I am confident that I would ...
This letter is to express my interest in the position as Systems Engineer for International Widget Corporation in South America, announced in the December job ...
This letter is to express my interest in the Customer Service Manager position posted on the XYZ Company web site. Your marketing department has advertised ...
March 22, 2007. This letter is to express my interest in discussing a position with your firm. I believe an opportunity with your firm will provide me with priceless ...