Напр.

"Objective resume section
The Objective resume section includes the name of the company you are applying to, the position you are applying for and a statement about how you can help a company meet its goals. This section is user centered. In other words, avoid making a statement that focuses on you or that sounds like you are trying to use the company to further your own career. Instead, get specific with the company name and its goals.

The Objective resume section is optional. The information commonly written within it also fits easily into your cover letter, so only use an objective section if you feel it adds to the quality of your resume."

http://www.write.com/writing-guides/job-search-writing/resume-sections/the-standard-resume-sections/

с уточнением:

\\\ В теме письма что-нибудь типа
\\\ ххх position application

вот именно это "ххх [position] application" и выносистся в сабж.
(а в теле письма - собственно письмо, т.е. cover letter)

ххх тупо берется из объявления