If you do a Google search on how to write the “perfect” cover letter, you’ll probably see articles saying that the cover letter is obsolete. This would be because most employers prefer to read a perfectly crafted email in which you could explain the same things as in the cover letter.
I quite agree with this up to a point. The e-mail is extremely important, but so is the cover letter.
– you apply for job X at company Y. The email address to send your application is email@example.com. In this case, you should focus on the cover letter. In a generalist email like this, nobody will read the text in the body of the message. Don’t bother with it.
– you apply for job X at company Y. The email address to send your application is firstname.lastname@example.org. In this case, you have the semi-private email address of the person in charge of the recruitment. Focus on both the cover letter and the email. The person might not download the cover letter or stop to read your email. You should cover all bases because of this.
– you apply for job X at company Y. The email address to send your application is email@example.com. After being sure the person is really the one recruiting and that the company exists, write an extraordinary email to which you should attach an even more extraordinary CV, short and to the point.
The “4th situation” is applying through LinkedIn, but that`s for a future post.
In all situation, focus on “SEO”. Use Bold and Italic to highlight some keywords in the email/cover letter. But don’t overdo it. The principle behind it is to make the text easier to read by the recruiter/director etc.